With their leading scorer Jonas already suspended, Benfica are sweating on the fitness of their biggest creative threat Nicolas Gaitan ahead of their Champions League quarter-final, second leg against Bayern Munich.

The teams meet at the Estadio da Luz on Wednesday with German champions Bayern defending a 1-0 first-leg lead after an early Arturo Vidal goal last week.

It is not a comfortable advantage for Pep Guardiola's side, but Benfica are still up against it, all the more so with their 32-goal Brazilian forward Jonas ruled out of the clash in Lisbon after being booked in the first leg.

Benfica still have an in-form striker to call on in Greek international Kostas Mitroglou, but Argentine star Gaitan, a brilliant attacking midfielder who has four Champions League goals this season, is struggling with a thigh injury and would be a big miss.

"We will make a decision tomorrow. We will need to wait until kick-off time to see if he is available," Benfica coach Rui Vitoria told a press conference on the eve of the game.

"We managed to ensure that the tie will be decided at home but it will still be extremely difficult for us to go through," he added.

"We will be coming up against a very strong team who are used to playing in matches like these and are contenders to win the trophy."

Portuguese league leaders Benfica are in tremendous form as they look to reach the semi-finals in Europe's elite club competition for the first time since 1990, when they reached the final before losing to AC Milan.

Bayern, in contrast, have been experts in reaching the latter stages of the Champions League in recent times, making it to the semi-finals at least in five of the last six campaigns.

Guardiola knows an away goal would silence the Benfica fans who are expected to fill the 65,000-seat Estadio da Luz, but the Spaniard is also focusing on making sure his men give nothing away.

"We will go out there to defend well and try to score a goal to go through," he told a press conference following Bayern's arrival in Portugal.

"Tactically we know what we need to do. Above all we will need to show great character in front of more than 60,000 spectators," added Guardiola, who saw his side lose to Porto on their last visit to Portugal last season before roaring back to win that quarter-final tie at home in the second leg.

Guardiola left behind defender Mehdi Benatia, who only returned to training with the rest of the squad on Monday after recovering from muscular problems sustained during the last international break.

In addition, long-term absentees Jerome Boateng, Arjen Robben and Holger Badstuber are on the sidelines.

The Bavarians have won all three previous two-legged confrontations with Benfica and have gone on to reach the final on each occasion, including on their way to winning the European Cup in 1976.