Josip Stanisic will miss the start of Bayern Munich's Bundesliga campaign after undergoing knee surgery.

The defender, who has returned to the club after a successful loan spell with Bundesliga champions Bayer Leverkusen, tore a collateral ligament in his right knee during training on Monday.

Stanisic, who started Bayern's 4-0 victory over Ulm in the DFB-Pokal last Friday, is set to be out for several weeks, according to a statement released by the club.

The Croatia international won the league and DFB-Pokal last season, making 20 appearances in the Bundesliga for Leverkusen during their unbeaten domestic run.

Vincent Kompany's men will kick off their top-flight campaign against Wolfsburg on Sunday. 

Bayer Leverkusen coach Xabi Alonso said his team deserve to win all three trophies available to them this season after they qualified for the Europa League final by seeing off Roma on Thursday.

Leverkusen, who have already wrapped up the Bundesliga title and will contest the DFB-Pokal final on May 25, stretched their unbeaten run through all competitions this season to 49 matches, surpassing Benfica's long-standing European top-tier record set between 1963 and 1965.

Once again, they did it the hard way after two Leandro Paredes penalties wiped out their first-leg advantage, with a Gianluca Mancini own goal and a stoppage-time strike from Josip Stanisic completing a dramatic comeback.

Following their 4-2 aggregate victory, Roma will face Atalanta in the May 22 final in Dublin, after La Dea overcame Marseille 4-1 on aggregate in the other semi-final.

"We'll play two finals in a week as a result," Alonso said. "We showed great character today after their second goal. 

"I looked my players in the eye afterwards and saw that they wanted more.

"We still have the chance to win three titles, and my boys deserve all three titles."

Despite going 3-2 up on aggregate when Mancini put through his own net, Leverkusen refused to sit back as they looked to preserve their unbeaten record, which they did through Stanisic's 97th-minute strike.

Asked whether that goal was one of the biggest moments of his career, the Bayern Munich loanee said: "Definitely one of them. 

"We knew what was at stake, we really wanted to get to the final and I think you could see that over 90 minutes today.

"I don't think we would have cared in the end if we lost and still progressed because we really wanted to get to the final, but it's even nicer this way."

For Roma, the chance to reach a second straight Europa League final after last season's defeat by Sevilla on penalties slipped away in the dying minutes of the match.

"When you manage to get it back from 2-0 down and go close to the miracle, knowing nobody has ever beaten them this season, it hurts to see us concede a goal like that. It hurts," Roma boss Daniele De Rossi told Sky Sports Italia.

Bayer Leverkusen reached the Europa League final and stretched their remarkable unbeaten run to 49 games on Thursday, Josip Stanisic scoring seven minutes into stoppage time in a dramatic 2-2 draw with Roma.

Having won last week's first leg 2-0 in Italy, Leverkusen were strong favourites to advance to this month's final in Dublin, though two Leandro Paredes penalties left them facing up to the prospect of extra time.

Paredes halved Leverkusen's aggregate lead on the stroke of half-time after Jonathan Tah fouled Sardar Azmoun, then repeated the trick following a bizarre handball from Adam Hlozek shortly after the hour mark.

However, Roma's hearts were broken as goalkeeper Mile Svilar – who was otherwise outstanding – failed to claim a routine corner and it bounced in off the unfortunate Gianluca Mancini with eight minutes of the 90 remaining. 

Rather than sitting back at 2-1 up in the tie, Leverkusen chased a leveller in order to preserve their unbeaten record across all competitions this season.

It was yet another last-gasp effort that kept that record intact, with Stanisic firing into the bottom-left corner after being played through by Granit Xhaka.

Xabi Alonso's team are now unbeaten in 49 games in all competitions, breaking Benfica's previous European top-tier record of 48 matches, set between 1963 and 1965.

Leverkusen will face another Italian side in the showpiece game, after Atalanta crushed Marseille 3-0 in Bergamo to seal a 4-1 aggregate win in the other semi-final.

In-form striker Gianluca Scamacca had already rattled the crossbar when La Dea took the lead, with Ademola Lookman's strike deflecting in off the unfortunate Samuel Gigot. 

Lookman then turned provider as Atalanta stretched their advantage seven minutes after the break, teeing up Matteo Ruggeri for a rasping finish into the top-right corner.

Gian Piero Gasperini's men were able to add some gloss to the scoreline at the death, with El Bilal Toure's pinpoint finish giving Pau Lopez no chance to round off a dominant win. 

West Ham were breached by two late goals as they slipped to a 2-0 defeat in the first leg of their Europa League quarter-final at Bayer Leverkusen.

The Hammers had defended heroically for 83 minutes before goalkeeper Lukasz Fabianski was finally beaten by substitute Jonas Hoffman.

A one-goal deficit might have given David Moyes’ side hope going into next week’s second leg at the London Stadium, despite facing a side unbeaten all season.

But disaster struck in stoppage time when a second substitute, Victor Boniface, headed home Hofmann’s cross, to leave West Ham’s hopes of a third consecutive European semi-final looking horribly slim.

A yellow card for Lucas Paqueta, ruling the Brazil international out of the second leg, only adds to the task facing the east Londoners.

The Hammers, without injured top scorer Jarrod Bowen and defensive midfield linchpin Edson Alvarez through suspension, were almost undone in the seventh minute when Josip Stanisic’s wayward shot was flicked towards goal by Patrik Schick but the ball went straight to Fabianski.

But Leverkusen were given a warning of West Ham’s prowess on the counter-attack moments later when Michail Antonio outstripped Jonathan Tah on the left wing and produced the best chance of the first half.

The burly frontman squared the ball to Mohammed Kudus, but the Ghana winger’s first-time strike was comfortably held by Matej Kovar.

However, West Ham were largely camped in their own penalty area and Fabianski palmed away Jeremie Frimpong’s curler before Exequiel Palacios’s drive was deflected over.

Paqueta’s over-enthusiastic challenge on Amine Adli earned him his booking – the Brazilian survived a red card check – and provoked a mild skirmish on the touchline.

Fabianski might have suspected he was in for a busy evening and he was proved right, making big saves to keep out dangerous efforts from Alejandro Grimaldo, Shick and Edmond Tapsoba.

Early in the second half Emerson Palmieri was shown a yellow card after catching Adli on the ankle, meaning the left-back will also sit out next week’s return leg.

Frimpong, a former Manchester City youngster, hit a low angled drive straight at Fabianski, before the 38-year-old Pole made a stunning save to tip Shick’s instinctive header over the crossbar.

But with seven minutes remaining Fabianski was powerless to prevent Hoffman’s shot bouncing through a sea of white shirts and into the net after a corner was only half-cleared.

Tomas Soucek cleared two Tah efforts off the line in a desperate finale before Boniface headed the second to leave the Hammers devastated.

Jeremie Frimpong fired into an empty net in stoppage time to cap Bayer Leverkusen’s outstanding 3-0 win over Bayern Munich as they celebrated carnival weekend in the Rhineland by moving five points clear at the top of the Bundesliga.

Josip Stanisic, the man on loan from Bayern, opened the scoring in the 18th minute before Alex Grimaldo doubled the advantage five minutes into the second half, but Frimpong added an exclamation mark after Manuel Neuer came up for a corner and Leverkusen broke to punish him.

Bayern had more of the ball but throughout the night it always felt as though Xabi Alonso’s side were the more dangerous, and this was a huge statement in their bid to win a first Bundesliga title and banish the nickname Vizekuzen – a mark of the five times they have finished runners-up.

The match at the BayArena kicked off eight minutes late after fans threw toy balls and other items onto the pitch as part of ongoing protests against the prospect of outside investment into the Bundesliga, and once play began it was Bayern who appeared to be on the front foot.

But while Leverkusen were happy to invite the visitors on to them, they were simply waiting for the moment to counter.

Their first shot at goal came in the 11th minute but Amine Adli’s effort lacked the power to trouble Neuer. Adli threatened again seven minutes later before Kim Min-jae got a foot in just in time, but Bayern were asleep from the resulting throw-in and were made to pay.

Robert Andrich drilled in a low ball across the face of goal and the Bayern defence stood still as Stanisic arrived to fire home, left all alone by Sacho Boey, usually a right-back but deployed on the left here in his second appearance since joining from Galatasaray last month.

Adli had a superb chance to get a second just before half-time as Granit Xhaka’s pin-point pass put him clean through on goal, but Dayot Upamecano recovered to get a toe on the ball, poking it back to Neuer.

It took only five minutes of the second half for the second to arrive. Grimaldo played a neat one-two with Nathan Tella to carve open the Bayern defence before beating Neuer at his near post with a rising shot.

Bayern were rocking, and there was chaos in their penalty area soon after, with Eric Dier’s cross hitting the arm of Leon Goretzka before bobbling back to Neuer, with a VAR check for handball coming to nothing.

Grimaldo hit the crossbar direct from a corner just after the hour as the ball dramatically dipped, but it bounced to safety.

Bayern tried to up the ante as Thomas Tuchel turned to his bench but struggled to create any real opportunities for a frustrated Harry Kane.

Instead, Leverkusen looked more likely to score again. Frimpong had already hit a post at the end of one late counter-attack, but had the final say after Neuer failed to get on the end of the corner and he raced down the pitch to fire into the unguarded net.