Barcelona admits any chance the Catalans have of overturning a 4-0 first-leg defeat to Bayern Munich in their Champions League semifinal return at home on Wednesday depends very much on the fitness of Lionel Messi.

The World Player of the Year looked out of sorts in Munich last week as an energetic display from the host tore Barca to pieces, but Messi did come off the bench to score a wonderful individual goal and set up a second for Alexis Sanchez in Barca’s 2-2 draw with Athletic Bilbao on Saturday.

And Barcelona assistant manager Jordi Roura believes Messi has started to find his feet again after being troubled by a hamstring injury for the past month.

“Messi is the best player in the world and obviously when you don’t have him you notice it. He makes the difference,” said Roura.

“He will continue with his recuperation after the injury. We hope that little by little he arrives at his best level. He will continue improving and the better Leo is the more chances we will have against Bayern.”

Bayern striker Thomas Mueller believes the Argentine star will be back to his brilliant best on Wednesday.

“In the first leg we barely saw him,” reflected Mueller, who scored twice and set up a third in the surprisingly lopsided first leg.

“That was down to us even if we know he was limited with an injury.

“We are going to see another Messi on Wednesday, even if we hope we don't. I think we'll have more work to do with him than the last time. “Messi is a talisman for them. He's a player who scores 50 goals in the season.”

Despite Messi not being at 100 per cent, Barca’s principal problem in the first-leg was its defending and manager Tito Vilanova has even more problems at the back with Jordi Alba suspended for Wednesday’s clash.

Adriano does return from suspension and is expected to replace Alba, however the biggest doubt remains who will partner Gerard Pique in central defence.

Javier Mascherano returned to light training on Monday well ahead of the schedule planned for him after suffering a lateral knee ligament injury against Paris Saint-Germain on April 2 and he could be thrown straight back into the side, although Vilanova also has the option of using either Eric Abidal or Alex Song.

Bayern by contrast will be able to welcome back striker Mario Mandzukic after he too missed the first-leg through suspension.

Risk-taking

And despite its comfortable lead, manager Jupp Heynckes has said he won’t rest any of his six first-team regulars who could miss the final should they be booked at the Camp Nou.

Captain Philip Lahm, Dante, Javi Martinez, Luis Gustavo, Bastian Schweinsteiger and Mario Gomez are all just one booking away from missing the showcase at Wembley should Bayern seal its passage into the final next month.

“I won’t be making any concessions,” Heynckes told the club’s website. “I’ll select my best available team. The players will have to show great discipline, which means: no gestures, no unnecessary fouls, and they mustn’t let themselves be provoked. That’s the decisive factor.”

And having once experienced losing a tie after winning the first-leg 5-1 when manager of Borussia Monchengladbach against Real Madrid in 1985, Heynckes is determined not to make the same mistake again. “We need the same attitude, willingness to run and good tactics,” he said.

Both Dante and Jerome Boateng missed training on Monday but both are expected to line up in central defence as German international Toni Kroos remains Bayern’s only absentee through injury.

More In: Football | Sport