Germany benefited from two own goals as they came from behind to seal a thumping 4-2 win over Portugal in Euro 2020 Group F on Saturday. 

Cristiano Ronaldo had put holders Portugal ahead early on with a strike that took him level with Miroslav Klose as the European player to have scored the most combined goals (19) across the World Cup and European Championship. 

Joachim Low's side stormed back before half-time, however, courtesy of two own goals in the space of four minutes from Ruben Dias and Raphael Guerreiro. 

The 2014 world champions wrapped up an emphatic first victory of the tournament in the second half thanks to strikes from Kai Havertz and the impressive Robin Gosens, with Diogo Jota pulling one back for Fernando Santos' men.  

Left-back Gosens thought he had handed Germany a fifth-minute lead but his acrobatic effort at the back post was ruled out for offside against Serge Gnabry.

Despite Germany's dominant start it was Portugal who struck first, Ronaldo tapping home from close range in the 15th minute following a flowing counter-attacking move involving Bernardo Silva and Jota. 

Germany pulled level 10 minutes before half-time, though, when Dias diverted Gosens' mis-hit volley past Rui Patricio from just outside the six-yard box. 

Things got even better for Joachim Low's side four minutes later when Guerreiro turned into his own net from close range after Joshua Kimmich had pulled the ball back across the face of goal.

They extended their lead further six minutes after the interval, Havertz turning in Gosens' cross from close range. 

Gosens then added his name to the scoresheet on the hour mark, leaping highest at the back post to head home Kimmich's cross from the right. 

Liverpool striker Jota gave Portugal hope of pulling off a memorable comeback when he fired home from Ronaldo's pull-back in the 67th minute, but Germany held on to inflict just a third defeat in their last 31 matches for Portugal. who hit the post late on through Renato Sanches.

Christian Pulisic admitted to being "very frustrated" at being left out of Chelsea's starting line-up for Wednesday's Champions League semi-final second leg with Real Madrid.

The United States international scored a crucial away goal for the Blues in last week's first leg but was named among the substitutes for the return fixture at Stamford Bridge.

He again made his impact known, however, by setting up a goal for Mason Mount 18 minutes after being introduced from the bench in the 2-0 win, which saw Chelsea through 3-1 on aggregate.

"I'm very frustrated," Pulisic, who has struggled with injuries this term, told CBS Sports. "There's not much else to say. I wanted to play from the beginning, as I always do.

"I've had to continue to prove myself over and over again. But, as always I reach out to God and he gives me strength. With that behind me, nothing can stop me really."

A look at the Opta stats shows Pulisic has a right to be frustrated, having now scored and assisted a combined four goals in the Champions League in nine appearances this term.

Only Olivier Giroud and Timo Werner have been directly involved in more (both six) - in eight and 11 games respectively.

For comparison, Mount - who has been superb for Chelsea this season - has three direct goal involvements in 10 Champions League games, while Kai Havertz has two from 11 respectively.

Focusing on the Premier League, meanwhile, Pulisic has four goals and one assist in 23 appearances this term, just 14 of those being starts.

Pulisic's average of a 0.26 goals per 90 minutes is slightly better than Havertz's return of 0.25 and behind only Giroud (0.5) and Tammy Abraham (0.52) among Chelsea's attackers. Werner, for context, averages 0.23.

The 22-year-old also performs better when it comes to chances created per 90 minutes in the English top flight when compared to Havertz - 1.37 to the German's 1.07.

But Pulisic still ranks some way below Hakim Ziyech, who has created 2.54 chances per 90 minutes this season and will also perhaps feel that he should be starting more often.

Mount (2.68) and Callum Hudson-Odoi (2.71) lead that particular metric, incidentally, which only highlights just how many options Thomas Tuchel has available in that zone.

One area Pulisic struggles in comparison to his attacking rivals is passing accuracy in the opposition half - 80.95, which is lower than Havertz's 84.3, Mount's 85.45 and Hudson-Odoi's 85.65. ​

The American's win rate when starting games also does not make for good reading.

The Blues have won 13 and lost just two of the 20 league games Pulisic has not featured from the beginning this term, compared to four wins and five losses in the 14 games he has been included in the XI.

Chelsea average 1.8 league goals with Pulisic in their starting line-up, as opposed to 1.3 without, while their average goals against rises from 0.6 to 1.4 when he starts.

Tuchel ultimately knows best when it comes to his team selection - and he is backed up by the possibility of a Champions League and FA Cup double - so Pulisic will simply have to keep proving himself if he is to hold down a regular starting spot.

Kai Havertz has all the qualities to be "world class" but was always likely to need time to settle in at Chelsea, according to Bayer Leverkusen's sporting director Simon Rolfes.  

The Blues spent a reported £72million (€80m) to bring the Germany international from Leverkusen in September, yet he has so far struggled to justify the hefty price tag.  

The attacking midfielder was one of several big-money signings during a busy close-reason recruitment drive, with compatriot Timo Werner - who arrived from RB Leipzig - also enduring a difficult start to life at Stamford Bridge. 

Havertz has managed five goals and five assists, as well as 23 chances created (1.4 per 90 minutes) and five big chances created (0.3 per 90) in 25 appearances so far in 2020-21.  

For comparison, during his final season at Leverkusen, he registered 18 goals (0.43 per 90), nine assists (0.21 per 90), 84 chances created (1.99 per 90), 20 big chances created (0.47 per 90) from 45 appearances.  

Chelsea's struggles on the pitch this term saw club legend Frank Lampard sacked and replaced by Thomas Tuchel, and Rolfes feels it is unfair to focus purely on Havertz, who he is backing to show his true abilities in the Premier League.

"It's always difficult if you change country and a little bit of a different style. That's the same if we sign players," Rolfes told Stats Perform News. 

"Some players need two days, some guys need half a year. For example, Moussa Diaby needs three-four months to adapt from France, although he was playing for PSG, to adapt to the Bundesliga.  

"You have to have in mind when you sign players, that not everybody is directly from the first day there.  

"I've followed Chelsea a little bit from a distance, but it's not only Kai or Timo Werner struggling a little bit, it's also the team – they expected more from the whole squad.  

"That's not so easy if it's not working in the team and you come in as a new player. It's much easier if the team is working and you step in your best position.  

"That's a process for Kai, to adapt to England and the Premier League. There is no doubt Kai is a fantastic player and has all the ability to play on the world-class level and although it's probably not his best six months, there is no doubt in my opinion."

"There is a spirit in the team but also the club – a dynamic in the last months and last years. That should lead us one day to a title, that's our big goal."

Bayer Leverkusen are one of Germany's biggest clubs, but not since the 1993 DFB-Pokal have they celebrated silverware.

Leverkusen have come close on numerous occasions in the Bundesliga – runners-up in 1997, 1999, 2000, 20002 and 2011, while they also reached the 2002 Champions League final, succumbing to Zinedine Zidane's iconic volley in Glasgow.

There were also runners-up appearances in the DFB-Pokal – 20002, 2009 and 2020. But an exciting and entertaining Leverkusen, even in the post-Kai Havertz era, are on the right track amid Bayern Munich's domestic and European dominance.

Leverkusen sporting director Simon Rolfes told Stats Perform News: "It's not easy if you're playing with the best team in the world – Bayern – but we have made a step forward and quite close to the top. We want to go forward. If it happens this year, fantastic. But we want to proceed and develop the squad, and mentality."

When star Havertz left for Chelsea at the start of the season in a transfer that could rise to €100million, and Kevin Volland joined Monaco, it left a noticeable hole at BayArena, where the pair scored 30 goals across all competitions in 2019-20.

But led by prodigy Florian Wirtz and a thrilling core of players, including Moussa Diaby, Leon Bailey and Nadiem Amiri, Leverkusen are continuing to challenge this term.

Leverkusen are third in the Bundesliga – three points behind RB Leipzig and 10 adrift of reigning champions Bayern – while Peter Bosz's side are preparing to face Young Boys in the Europa League last 32 and Rot-Weiss Essen in the DFB-Pokal round of 16.

With Havertz having departed, Leverkusen have a better goals/game ratio (2.5) through 26 games across all competitions this season, compared to 1.8 in 2019-20. The club have also improved defensively – goals conceded/game (1.0) and expected goals against (1.0) are better than last term (1.3) and (1.4) respectively.

Collecting 32 points, Leverkusen have played the best first half of a Bundesliga season for seven years – they collected 37 points at this stage in 2013-14.

Leverkusen have also exceeded their xG value of 23.1 to almost nine goals (8.9) – only Bayern have a greater margin between goals and xG (13.9). 

"In general yes because it's a chance for other players to develop and take more responsibility in the team and on the pitch," Rolfes, who was appointed in 2018, said when asked if he was always confident following the exits of Havertz and Volland. "We had the view that there could be other players who could take a step forward. The only thing for sure is Havertz is a world-class player, a fantastic guy and player. It's very difficult to replace him, so we said, it's not our direction to find a replacement for Kai because you will never find that replacement.

"We said okay, we will give our own players the chance to grow, this strategy works out very fast. It's always a risk for sure, but we have the confidence in those players to make a step forward, and also the team. If your superstar is gone, everyone knows we have to give more.

"We try to build-up, play offensive with ball possession, straightforward – the kind of style we showed against Borussia Dortmund [2-1 on January 19] is what we want. We want to have the ball, a lot of clubs and trainers are speaking to play without the ball, in Germany it's very popular, but we want to have the ball and want players who want the ball."

The emergence of teenage sensation Wirtz, and development of Diaby, Bailey, Edmond Tapsoba and Amiri, has further highlighted Leverkusen's successful recruitment and philosophy, which has become synonymous with German clubs.

"You have to have a clear strategy," Rolfes, who made almost 400 appearances for Leverkusen between 2005 and 2015, said. "A clear strategy of recruitment but also your playing style. That's really important for players but also the success of a club – both are strongly connected. For your playing style, you have to sign the right players. Then you have the chance that the players adapt quicker and develop better in your system because they feel comfortable in the way of playing. That's crucial.

"We know the Bundesliga, financially solid, but we are not at the top that we can sign every player, we have to develop players. The strategy is to recruit good players for our style and develop them to the top. Some clubs in Germany are quite successful with this."

"We are focusing on that talent and try to find them," he said. "We analyse millions of data with artificial intelligence, to pre-select and be early. It's not because we know players other clubs do not know, maybe 20 years ago, but everything is transparent. But you have to find them a bit quicker, but also clear in your playing style and what can they develop with your training work, in which areas they can develop in weak points. Because we are not signing players where everything is 100 per cent, we know they have weak points, but we know we have to work with them on that."

Data and AI continue to play a huge role in football, with Rolfes adding: "It's very important and because the data will be better and better, it will become much more important in the future because you will get better results. We are working with our own team on scouting, preparing for next matches – just in our daily work."

The likes of Michael Ballack, Toni Kroos, Bernd Leno and Havertz have all made names for themselves at Leverkusen, and Rolfes continued: "We count on the young players [at Leverkusen]. We give them trust and the opportunity to play. For example, Wirtz, we give him the chance to replace Havertz and not sign another star to put in front of him. That is one thing.

"We have a very professional environment, we really take care of the guys – try to develop them, work on the pitch and prepare them for top football. We have an advantage that the media surrounding is not so big here. That's good for young players to have a familiar environment where they feel very comfortable and less stressful, then try to reach the best level on the pitch."

Wirtz is the heir apparent to Havertz, having made an immediate impact after the 17-year-old swapped Cologne for Leverkusen in 2020.

Having made his debut in May 2020, Wirtz became the youngest goalscorer in Bundesliga history the following month, finding the net in a 4-2 defeat to Bayern after coming on as a substitute. Dortmund's Youssoufa Moukoko has since snatched that record.

Among all players with at least 50 dribbles in this season's Bundesliga, only Augsburg's Daniel Caligiuri has a better dribbles success rate (70 per cent) than Wirtz (65 per cent). 

Wirtz is one of 50 players born in 2003 or earlier to appear in Europe's top five leagues this season. Those 50 players have collected a total of 14 goal involvements – with seven of them coming from Wirtz. 

Among all players in Europe's top five leagues born in 2003 or earlier, Wirtz played the most minutes in all competitions this season (1,579) and had the most goal involvements in all comps (11 – six goals and five assists). 

"I saw him for the first time at 13. Now I have to say, he is playing Bundesliga the same way he was playing at 13, 14, 15, 16 – I followed him all the years. I always said okay, that's the player for us, the player for Leverkusen. That was not a surprise for me when he came to us and adapted very quick to our style," former Germany international Rolfes said.

"It was also one argument I said to him during the transfer. I said, 'you are a player for us, you will develop your skills and strengths much better because that's what we need in our style'. His development is fantastic."

Like Havertz, Bailey could be the next Leverkusen star to leave amid constant speculation over his future.

The 23-year-old winger, who has scored four goals and supplied five assists in the 2020-21 Bundesliga so far, has been linked with the likes of Manchester United and Manchester City and Rolfes is unwilling to sell the Jamaican to just any club.

"He's played a fantastic season," Rolfes said. "He struggled a bit last season, but he is performing at a very high level. A good guy in the squad. He has a chance to score goals for sure. A fantastic technique. That's part of lives also, to sell players but we want to sell to the top eight clubs in the world, but not to other clubs. Sometimes a player will leave us. We have a contract with Bailey but we are quite relaxed."

Diaby is another prime example for Leverkusen, where the accelerating Frenchman has 561 sprints in the league this season, more than any other player. 

The former Paris Saint-Germain speedster has been involved in 15 goals in all competitions in this season (in 26 games) – with his next goal involvement the 21-year-old would already reach his value from his first season in Leverkusen (16 in 39 games). 

"When we extended the contract until 2025, that was a really nice Christmas present to extend the contracts of Diaby, Tapsoba and Wirtz," Rolfes said. "[Diaby] is a key player of our squad. His acceleration and speed is outstanding. He has developed on scoring and assisting. To use his acceleration on a top, top level. He has potential to develop further. I'm very, very happy he is part of our squad."

Meanwhile, Timothy Fosu-Mensah could be the latest success story for Leverkusen, who also completed the signing of Netherlands Under-20 international Jeremie Frimpong from Celtic on Wednesday.

After joining Manchester United's academy in 2014, the 23-year-old called time on his Old Trafford stay in January, and Rolfes said: "He is not so young but the last two years, you had the feeling there was more in the box than there was in the last two years. That's interesting for us, to sign that kind of player where you have the feeling they can reach more. We want to help him.

"Timothy is a really good guy, ambitious guy. I like this. He has the ability, the physicality, very fast, a good technique. A lot of fundamental things that are important for our playing style. Then if the mentality and ambition isn't right, then let's work on that to develop you. I'm convinced Timothy can be the next example for our club."

It did not take long for Chelsea to run out of patience with Frank Lampard following significant investment in their first-team squad during the close season.

Chelsea spent in excess of £200million on reinforcements for the 2020-21 campaign but with the club ninth in the Premier League and 11 points off top at the midway point, they dispensed with the services of their head coach on Monday.

Lampard arrived just 18 months ago with the club under a transfer embargo and was lauded for his faith in youth during a debut campaign that yielded a top-four finish and an FA Cup final appearance.

However, Chelsea have not managed to maintain an upward trajectory this season and after a run of two wins in eight Premier League games the decision was taken to cut ties with the club legend.

It is fair to say some of Chelsea's new arrivals have not lived up to expectations this term and we look at the numbers behind their performances.

Timo Werner – £45m from RB Leipzig

Werner arrived from Leipzig with big expectations having been involved in 36 league goals (26 scored, eight assisted) in 2019-20 – a tally only bettered by Robert Lewandowski (38), Ciro Immobile (45) and Lionel Messi (46).

He did not take long to find his stride, having a hand in 11 goals (eight scored, three assisted) in a 10-game stretch in all competitions between September and November.

However, the only goal he has scored in 15 appearances since the end of that streak came against Morecambe in the FA Cup third round – it ended an 827-minute drought in all competitions.

He is without a goal in 11 Premier League outings and his difficulties in front were compounded by his failure to convert from the penalty spot against Luton Town on Sunday.

Kai Havertz – £71m from Bayer Leverkusen

Alongside Werner (14) and Tammy Abraham (15), Havertz (10) is one of just three Chelsea players to have been involved in at least 10 goals in all competitions this season.

However, half of those have come against lower-league opposition – he scored the first hat-trick of his senior career against Barnsley in the EFL Cup in September, and versus Morecambe in the FA Cup this month had a goal and an assist.

When looking at his figures from the Premier League, he has just one goal and one assist in 16 appearances – 11 of which have come from the start.

Lampard seemed to struggle to figure out how to get the best out of versatile forward Havertz and given his price tag that will be high on the agenda for his replacement.

Ben Chilwell - £45m from Leicester City

A plantar fascia injury delayed Chilwell's Chelsea debut but he was quick to make an impact, becoming just the third Blues player to both score and assist on their Premier League debut, joining Deco and Alvaro Morata.

Within 13 games he had already matched his career best of four Premier League assists in a single season, while his six goal involvements in that time frame was the same as he managed across the entirety of 2019-20 for Leicester.

Crosses from the full-backs were a key part of Lampard's approach and Chilwell's 82 in open play is second to Reece James' 97.

But while 24.7 per cent of James' deliveries were accurate, only 13.4 of Chilwell's were - the third-worst rate of any Blues player to find a team-mate with at least one cross in open play.

Hakim Ziyech – £33.3m from Ajax

An assist for Werner in a pre-season friendly against Brighton provided promising signs, but a knee injury meant his competitive debut did not arrive until October.

He has registered two goals and four assists in 17 appearances in all competitions, but only Mason Mount (2.5) has created more chances per 90 minutes than Ziyech (2.4) this season (all comps).

Furthermore, he creates 0.8 Opta-defined 'big chances' per 90 minutes, which is the most of any Chelsea player to have featured in more than two games.

His expected assists in open play per 90 minutes of 0.21 ranks joint-seventh alongside Kevin De Bruyne (among players to have played at least 450 minutes), so with some better finishing his impact may look more impressive on paper.

Edouard Mendy – £22m from Rennes

After Kepa Arrizabalaga committed three errors leading to goals in as many Premier League appearances to start the season, bringing in Mendy from Rennes appeared an astute decision.

He kept nine clean sheets in his first 12 appearances in all competitions, but in his subsequent nine outings he has shut out the opposition just twice and conceded 13 goals.

In the Premier League, Mendy has let in 12 goals from an expected goals on target (xGOT) of 10.8, meaning he has let in one more goal than would have been anticipated from the chances he has faced.

That is the joint-eighth worst in the league among keepers to have played over 900 minutes.

Thiago Silva – free transfer

Although he became the first outfield player to make an error leading to a goal on their Premier League debut in two years when his loose control was seized upon by Callum Robinson in a 3-3 draw with West Brom in September, Silva's experience seemed to significantly improve Chelsea's defence.

Only Kurt Zouma (64.6 per cent) has a better duel success rate than Silva's 63.5 among players to have played at least 10 games in all competitions, and he has helped them tighten up when defending set-pieces.

Excluding goals scored directly from free-kicks, Chelsea conceded 13 times from set-pieces in the Premier League in 2019-20, while this term they have only shipped five from dead balls and one of those came when Silva was not in the side.

The Brazilian has also made them more of a threat from set-plays, providing two of the nine goals Chelsea have scored in such situations.

Chelsea boss Frank Lampard hopes Kai Havertz and Timo Werner will gain confidence from scoring in the FA Cup win over Morecambe.

Werner ended a goal drought of 827 minutes with the home side's second in a 4-0 triumph at Stamford Bridge on Sunday, Mason Mount having opened the scoring.

Havertz was involved in his fellow German's goal just before the break and went on to find the net himself against fourth-tier opposition, heading in a cross from Cesar Azpilicueta in the 85th minute.

The duo were part of a strong team selected by Lampard, who believes the big-money signings from the Bundesliga made a "nice little step" forward as they continue to adapt to life at Chelsea.

Discussing Werner, who had not scored for his club since a 4-1 win over Sheffield United on November 7, Lampard said: "I'm pleased for him.

"Strikers want to score goals and he's had plenty of near misses in those times. He's been getting in positions to score goals but they haven't been going in for him.

"I was pleased to play him today and get him confidence from scoring a goal. It wasn't easy, there wasn't space behind them because they defended so deep, but he gets his goal and moves onwards.

"It's important that we understand with both Timo and Kai that they are young lads coming into this league. Tough patches are normal coming into the Premier League - some of the greatest players that have graced it have found that at the beginning.

"That is a nice little step for both of them."

While Werner made way for Olivier Giroud in the 68th minute, Havertz played the full game, during which he completed 89 per cent of his attempted passes.

The former Bayer Leverkusen player also had two shots as he continues to build up his fitness after overcoming COVID-19, with Lampard insisting Chelsea fans must show some patience with the 21-year-old.

"There are numerous levels Kai can go up because of the potential of him as a player," Lampard told the media.

"Even in his short period at Chelsea he's been unfortunate in that he had COVID and suffered a bit in coming back from that.

"Today I saw him - and during the week in training too - looking stronger and fitter. There are levels to go up, but - again - we have to remain patient.

"He's come here with a huge amount of talent but has to get accustomed to the league, accustomed to the speed of the league, the pace of the league. We as a club must support him through that for the future, both him and Timo.

"It was a small step in a big picture, but a step made in a good way for both of them."

The victory means Chelsea have progressed in their third-round tie in every season since 1997-98, when they were eliminated by Manchester United.

Chelsea eased into the fourth round of the FA Cup with a 4-0 win over Morecambe on Sunday to end a three-match run without a victory.

Perhaps in a sign of the growing pressure on his position after a run of one win in seven games in all competitions, Frank Lampard named a very strong team for the visit of the League Two side to Stamford Bridge.

Mason Mount's fine strike on the midfielder's 22nd birthday opened the scoring before Timo Werner ended a goal drought of 827 minutes shortly before half-time.

Callum Hudson-Odoi got his side's third and only goalkeeper Mark Halstead denied the Blues further goals until Kai Havertz powered in a late header.

Morecambe almost snatched a shock lead with 11 minutes played, Kepa Arrizabalaga - on his 100th Chelsea appearance - doing well to stop Adam Phillips' drilled cross from going over the line.

Chelsea's breakthrough came with 18 minutes gone, Mount given time to pick his spot from 20 yards out, leaving goalkeeper Halstead with little chance.

Werner had missed an early header but could not pass up the chance to make it 2-0 just before half-time, the forward prodding into an empty net after Havertz headed back across goal.

Any lingering doubts about the result were removed four minutes after the restart, Hakim Ziyech's pass beating the offside trap and allowing Hudson-Odoi to power a shot through Halstead.

Havertz should have made it 4-0 only for Halstead to block at the near post and the keeper made a second fine stop to deny Christian Pulisic on the rebound, the keeper's best moment of a good display.

He could do nothing to prevent Haverz from finding the back of the net five minutes from time, though, the midfielder meeting Cesar Azpilicueta's deep cross with a thumping header.
 

What does it mean? Light relief for Lampard ahead of testing run

It would have been an almighty shock had Morecambe become the first team since Manchester United in 1997-98 to knock Chelsea out of the competition in the third round.

Lampard took no chances, fielding a formidable line-up against a fourth-tier side who had to isolate for 10 days after a coronavirus outbreak in late December.

The Blues sealed a comfortable win that will have lifted spirits ahead of a run of five league games that includes visits to Fulham, Leicester City and Tottenham.

Ziyech enjoys roaming role

His shooting was a little wayward but Ziyech was certainly precise with his passing, albeit against modest opposition who only returned to training this week.

He made more passes in the Morecambe half (56) and created more chances (four) than any other Chelsea player in his 67 minutes on the pitch.

Can Werner kick on?

It will have been a relief for Werner to score his first goal since November, but there was still a feeling of disconnect between the striker and his supporting cast and he only completed one more pass (14) than goalkeeper Kepa.

Lampard will have hoped to give the £47.5million man a confidence boost. Time will tell if it worked.

What's next?

Chelsea return to league duties at Fulham next Friday in a west London derby, with the game at Leicester to follow on January 19.

Kai Havertz was dubbed the 'Crown Prince of German football' while at Bayer Leverkusen but the Bundesliga club have a new star now: Florian Wirtz.  

While his former club colleague has struggled so far to make an impact at Chelsea, Wirtz - the latest young gem to come through at Leverkusen - is dazzling for Peter Bosz's team, who remain ensconced in the top four despite defeats either side of the mid-season break in Germany's top flight. 

The 17-year-old did not wait long to suggest he could be the heir apparent, either. Having made his debut in May 2020, he became the youngest goalscorer in Bundesliga history the following month, finding the net in a 4-2 defeat to Bayern Munich after coming on as a substitute. Youssoufa Moukoko has since snatched that record away.

This season, Wirtz has gone from the periphery to centre stage, scoring twice and providing four assists in 13 appearances. His transition from promising talent to first-team regular has been swift, leading to comparisons to Havertz, the playmaker who swapped the BayArena for Stamford Bridge.

However, for Bosz, while both players have huge potential, the duo differ in so many ways.

"I never compare players with each other because that is impossible. There is no player like the other," Bosz told Stats Perform News. "You can't compare them. That's not possible.

"I also won't do that with Florian Wirtz, because he has his own style. He is different from Kai Havertz, who is more of a striker. Florian Wirtz, as far as I am concerned, is a midfielder, so you can't compare them.

"Also, you can't compare them physically; Kai is 1.92metres (6ft 3in), Florian is shorter. One is left-footed, the other one right-footed. They both have their own style. But both of them are very good. Both are very talented. Both have a huge career ahead of them.

"And Florian is only 17 years old. What he has shown though in the Bundesliga already is something special."

Wirtz has been a part of a Leverkusen squad that has impressed so far in this campaign, both at home and abroad. 

Despite a first defeat to Bayern Munich before the mid-season pause in Germany, Leverkusen gathered 28 points from their opening 13 league games. Only three times have they managed to collect more points across the same period - and on each of those occasions they went on to finish in the top four.

In the Europa League, Die Werkself finished top of Group C to qualify for the last 32 in style, winning five of their six round-robin fixtures. Having reached the quarter-final stage of the competition last year, when they lost 2-1 to Inter, hopes are high they can go further this time around. 

But while there has been much to please Bosz and Leverkusen's supporters so far, the Dutch coach insists there is still plenty more to come from his squad.

"Everyone still has some space to improve," he said, insisting no player has reached a nine out of 10 yet. "The difference to last year is that we are very consistent now.

"We deliver stable performances. It means that we concede less goals. We stand more compact on the pitch.  

"But we have also lost important players. Kai Havertz went to Chelsea, Kevin Volland to Monaco. I think that our team spirit has improved. This is the biggest step ahead." 

Despite Havertz no longer being around, Leverkusen have been excellent going forward, with champions Bayern the only team to score more in the Bundesliga so far. Their attacking intent has not come at a considerable cost defensively either - only second-placed RB Leipzig have conceded fewer goals.

The emergence of Wirtz has been one of the factors in helping Leverkusen continue to progress as a club, even with those key departures in the previous transfer window.

"He's a very talented young player. He has a lot more to improve. But, you know, he's only 17," Leverkusen winger Leon Bailey told Stats Perform News about his talented young team-mate.

"He's still learning. But he has a lot of qualities that a lot of older players don't have yet. And that's something you can see clearly, and this is something that's special. 

"And I think, as the years go by, he will only get better. There is a lot more to come from him, as he understands more and get a lot more experience.  

"I would say he's very smart. He has a lot of quality when he's on the ball. And he has a great passing ability."

Bailey's assessment is backed up by Wirtz's output, with no Leverkusen player having created more chances from open play than his tally of 23. While his passing accuracy is perhaps lower than might be hoped for at 73 per cent, his touches in the opposing box (31) and passes into the final third (55) are examples of his forward thinking when in possession. 

Those risks have reaped their rewards this term too, considering his six goal contributions so far. Bosz clearly has faith in him, as only goalkeeper Lukas Hradecky and Moussa Diaby have played more minutes in the Bundesliga so far. 

Any suggestion of becoming the new Havertz may be wide of the mark, but the future looks bright for Wirtz, the latest jewel to emerge at Leverkusen.