A sliding doors moment kept Mauricio Pochettino and Lionel Messi apart in 2005. But 15 years later, their paths could well realign at Paris Saint-Germain.

Back when Messi was in the embryonic stages of a Barcelona career that has seen him win six Ballons d'Or, 34 trophies and score a world record 644 goals for a single club, a temporary switch to cross-town rivals Espanyol was mooted.

There he would have linked up with an uncompromising defender by the name of Pochettino, and the subsequent decade and a half could have turned out very differently.

"I remember that summer, he was so close to moving to Espanyol," Pochettino said ahead of Tottenham facing Messi's Barcelona at Wembley in a Champions League clash in October 2018.

"If he did, maybe he could have been the biggest star in Espanyol. We should be the Barcelona! He would have been my team-mate and maybe I would still be in Espanyol managing him."

It only would have been a loan move, but an 18-year-old Messi convinced Barca he was ready for a more prominent role in the team by producing a stunning display in a victory over Juventus in the Joan Gamper Trophy.

Fabio Capello was in the opposition dugout at Camp Nou and after 25 awestruck minutes, he approached his counterpart Frank Rijkaard to ask if he could take the Argentine wonderkid on a temporary deal.

Barca finally realised they had a generational talent on their hands and opted against letting him go.

"I'd started to hear about Messi when I was an Espanyol player – this small guy playing in the Barcelona academy, who had arrived from Argentina when he was 13," Pochettino said.

"And then I heard he was very close to signing for Espanyol. But because he was so fantastic in the Joan Gamper against Juventus and Fabio Capello praised him afterwards in the press conference, Barcelona changed their minds. They kept Messi at Barcelona."

2030 vision

Messi began his youth career with Newell's Old Boys in 1994 – the same year Pochettino left the club for his first stint with Espanyol – and has often been linked with a return to the Rosario side to end his playing career.

Pochettino has been out of work since being sacked by Tottenham in November 2019 and was reportedly approached by Barcelona to replace Ernesto Valverde two months later, but his request for more time to consider the offer due to his loyalties to Espanyol resulted in Quique Setien getting the job instead.

Still, Pochettino retained hope that he will still have an opportunity to join forces Messi.

"I want to return to Newell's with Messi," he told Radio del Plata last March. "I can still wait, [for an opportunity] and the best [possible scenario] would be in 10 years with Messi."

But with PSG's decision-makers showing minimal festive cheers by firing Thomas Tuchel on Tuesday, Pochettino has been gifted a potential opportunity to work with Messi far sooner.

Pochettino was on Saturday named as the successor to Tuchel. Sporting director Leonardo and president Nasser Al Khelaifi will no doubt hope his appointment helps tempt Messi to forego a reunion with Pep Guardiola at Manchester City and relocate to Paris when his Barcelona contract expires at the end of the season.

"He's one of the gods of football"

Pochettino may not have won a trophy with Tottenham, but he led them to four straight top-four finishes in the Premier League.

His crowning achievement was steering them to the 2019 Champions League final, which ended in a 2-0 defeat to Liverpool.

Spurs finished behind Barcelona in the group stage that season. Messi scored a double in a 4-2 win for the Blaugrana at Wembley, while a 1-1 draw at Camp Nou saw Pochettino's men edge Inter to the runners-up spot in Group B.

After Spurs lost the first leg of their semi-final to Ajax 1-0, Pochettino urged his team to play like Messi during the second leg in order to have another chance of taking on the Barcelona captain in the final.

"He's one of the gods of football. It's unbelievable, it's unbelievable. It's unbelievable, the desire and the capacity to fight with the ball at his feet, to fight without the ball at his feet," said Pochettino.

"What happens when he touches the ball? When he doesn't have the ball, it's unbelievable the character, how he presses, how he works for the team. If we play like him, for sure we are going to have a chance. Of course.

"But not like him doing what he does with the ball. If we play like him without the ball, with the desire that he showed, for sure we are going to have a chance to qualify for the final. If not no chance."

Should Pochettino's desire to work with "one of the gods of football" at long last become reality, together they will be expected to help PSG finally conquer their Mount Olympus: winning the Champions League.

Finally, 2020 is history - there won't be many people who aren't happy to see the back of a difficult year.

While the coronavirus pandemic shows no sign of making a swift exit, the turn of the year at least gives us the chance to look forward, and the same is true in the world of sport.

2020 saw many promising young players make the step up, some undoubtedly down to the absences caused by coronavirus or the packed schedule that the pandemic has led to.

We've picked out 21 under-21 players to keep an eye on in 2021 - and while you may already be familiar with some of them, there's good reason to give them your attention this year...

Illan Meslier, 20 - Leeds United

Few goalkeepers can come away from a 6-2 defeat having impressed, but Meslier did so against Manchester United recently. His eight saves prevented Leeds' crushing loss from getting even more embarrassing, while only three goalkeepers have produced more in a single Premier League match this term. His total of 63 is also the second most in the division – the France Under-21 talent, who joined on a permanent deal from Lorient last year, appears to have a big future ahead of him.

Kristoffer Klaesson, 20 - Valerenga

Goalkeepers tend to break through a little later than outfield players, but Norway youth international Klaesson has already been first-choice at Valerenga for the best part of 16 months – he only turned 20 in November. Coincidentally, he could have become a team-mate of Meslier's in 2020 as Leeds were reportedly interested, but he remains in Norway for the time being.

William Saliba, 19 - Arsenal

Saliba is certainly one of the most recognisable names on this list – after all, he has been owned by Arsenal for getting on for two years. Unfortunately, he has not been afforded much of a chance by Mikel Arteta this term, which makes him an interesting prospect to watch in 2021. Either he'll eventually get an opportunity at the Gunners, or a loan move will provide him with a crack at first-team football. After a tricky 2020, he'll want to get his career back on track.

Perr Schuurs, 21 - Ajax

Given his appearance, playing style and the fact he has come through Ajax's academy, comparisons between Schuurs and Matthijs de Ligt were to be expected. He may not reach the Juventus star's level, but he has certainly shown real promise that is reportedly interesting Liverpool. Schuurs is one of the five youngest players to have featured for at least 500 minutes in this season's Champions League, while his 47 ball recoveries was the sixth highest of any player in the group stage.

Ethan Laird, 19 - Manchester United

Aaron Wan-Bissaka was supposed to fix Man United's issues at right-back, but this season his defensive positioning has been concerning and he appears to have become even less effective in attack – his chances created and open-play crosses per 90 minutes have decreased significantly. Laird has long been considered a fine prospect at United and boasts the technical abilities to be a threat in attack. If he can stay fit, chances could be in the offing.

Tariq Lamptey, 20 - Brighton and Hove Albion

Having joined Brighton last January from Chelsea, Lamptey has quickly made a name for himself as an exciting wing-back. Last year saw the diminutive talent enjoy something of a breakthrough, but in 2021 he'll be looking to truly establish himself and potentially break into the England squad. There are few more exhilarating full-backs in the Premier League – his 3.8 dribbles per game is the third most among defenders to have featured more than twice.

Nuno Mendes, 18 - Sporting CP

Sporting have a wealth of talent coming through at the moment and left-back Mendes is arguably chief among them. Blessed with fine technical abilities, the 18-year-old is apparently a target for Man United, Liverpool and Real Madrid. Already a regular having started 10 of the Primeira Liga leaders' 11 games this term, Mendes' 10 completed dribbles is the fourth-highest among defenders in the division, while his 28 interceptions is second only to team-mate Luis Neto.

Gabriel Menino, 20 - Palmeiras

An intriguing player with a well-rounded skillset, Menino has already transitioned from centre-back to defensive midfield to right-back despite his young age. It is in the latter position where he impressed enough to earn a first Brazil call-up last year and only two players have provided more than his five assists in the 2020 Brazilian Serie A.

Moises Caicedo, 19 - Independiente del Valle

The past month or so has seen Caicedo brought to the attention of a wider audience – or, more specifically, Manchester United fans. The all-action midfielder was the teenager with the most goals (four), shots attempted (24), chances created (19), successful passes (748) and dribbles completed (23) in Ecuador's top flight in 2020, while his passing accuracy of 90.1 per cent was the highest among players to attempt 500 or more.

Billy Gilmour, 19 - Chelsea

Scottish talent Gilmour had shown real promise during his 11 Chelsea appearances last season before a knee injury in July laid him low. He returned to action last month with a few cameos off the bench, and there will be plenty hoping he can return to his previous level quickly. A loan move might be on the cards, but Frank Lampard has high hopes for the crafty midfielder.

Yunus Musah, 18 - Valencia

Valencia are going through another difficult spell, with off-field matters often overshadowing on-pitch performances. Nevertheless, in United States international Musah, they appear to have a reason for optimism. Another tricky winger, Musah's 38 dribbles is the second most among Los Che players this term and he became their youngest LaLiga goalscorer (17 years, 338 days) this century when netting back in November. He's one that got away from Arsenal.

Ander Barrenetxea, 18 - Real Sociedad

A nimble right-footed left-winger, Barrenetxea broke into La Real's senior side last season with 17 appearances in LaLiga. His eight starts this term is already an increase of five on the entirety of 2019-20 and he has been using that extra time on the pitch to excite. He has attempted 41 dribbles in LaLiga, and his 56 per cent completion rate is bettered by only seven players – all of whom are much older – among those to have tried at least 40.

Bryan Gil, 19 - Eibar (on loan from Sevilla)

If Barrenetxea embodies the modern 'inverted winger' style, then Bryan is very much a wide midfielder of the classic variety. A direct touchline-hugger, the left-winger's aim is almost always to beat his man and get a cross into the box, and he is catching the eye on loan at Eibar this term. Only five wingers in LaLiga can better Bryan's 49 open-play deliveries, though his 22.5 per cent accuracy is better than all but one of those with more cross attempts. He's also tried 44 dribbles, his 52.3 per cent completion putting him close to Barrenetxea.

Jaminton Campaz, 20 - Deportes Tolima

Campaz may not be a household name yet, but a move to Europe or one of South America's leading leagues is surely not far away. The attacker, who can play wide or through the middle, is an explosive player but also productive. No younger player had more goal involvements (five goals and four assists) and chances created (32) in Colombia's top division than Campaz.

Amad Diallo, 18 - Manchester United

Although United splashed a reported £19million on Diallo, the young Ivorian remains something of an unknown quantity. A left-footed right-winger, he has only been given a handful of opportunities in Atalanta's senior side – though he has often caught the eye with his ability on the ball. Given United's lack of options on the right flank, he might just establish himself sooner than some expect – either way, he will be one to monitor.

Pedri, 18 - Barcelona

As each week passes, more and more Pedri looks to be settling into the role as Lionel Messi's heir at Barcelona, but whether he's ready to take up such a mantle as early as this year is another matter. Messi's contract ends in June and so he could well depart – taking on his creative burden would be an unenviable task for a teenager, though Pedri is proving effective. He is creating a chance every 45 minutes on average in the league this term, the third most frequent in the squad among those to have played at least five times.

Talles Magno, 18 - Vasco da Gama

Are you really a Brazilian 'wonderkid' if you've not been linked with every major European club? Talles Magno fits the bill there and it's easy to see why there's interest. His end product still needs work, but his ability to excite is considerable – the 18-year-old has completed more than twice as many dribbles (106) as any other teenager in Brazil's Serie A between 2019 and 2020.

Karim Adeyemi, 18 - Salzburg

There has been a buzz around Adeyemi for a few years now as has previously impressed scouts with Germany's youth sides and during a fruitful loan spell at Liefering. Now back at Salzburg, he looks destined to be another serious talent off the club's impressive conveyor belt. Adeyemi is the only player to have been involved in four goals in a single Austrian Bundesliga this term, scoring and getting a hat-trick of assists in the 8-2 victory over St. Polten, while he set up a goal on his league debut for the club in June. A thrilling talent with great vision and dribbling abilities, Adeyemi may get even greater responsibility in 2021 following the departure of Dominik Szoboszlai.

Marcos Leonardo, 17 - Santos

It's still early days for Marcos Leonardo, though Santos clearly rate him highly – the striker's release clause is €100m. He's already the underage player with the most minutes played (296) and goals (one) in Brazil's top division this season, while he became the sixth youngest player to net in the Copa Libertadores (17y, 173d) when scoring a winner against Defensa y Justicia.

Youssoufa Moukoko, 16 - Borussia Dortmund

There's not much that hasn't already been said about Moukoko. He became the Bundesliga's youngest ever player in November when making his debut a day after his 16th birthday, before then also setting a new record for the league's youngest goalscorer in December. New coach Edin Terzic has already given him two starts – his next target will be to break records on the international stage with Germany. He couldn't get into their Euros squad, could he?

Matias Arezo, 18 - River Plate (URU)

Stocky, technically gifted and already proving decisive in front of goal with seven goal involvements (five goals, two assists) in 15 league matches, Arezo has a lot going in his favour. Whether he has the mentality or focus to not let the 'new Luis Suarez' labels distract him remains to be seen, but he's already the youngest Uruguayan (17y, 349d) to ever score a brace in the Copa Sudamericana having done so against Atletico Nacional in November.