Bayern Munich are likely to be without Franck Ribery as they aim to
overturn Porto's two-goal advantage in the Champions League last-eight.
The France forward, 32, is not fit enough to play after missing the past six weeks with an ankle injury.
However, Germany midfielder Bastian Schweinsteiger could return after missing the first leg with a virus.
Porto, who won 3-1 in their home leg, are missing Brazil defenders Danilo and Alex Sandro through suspension.
But the Portuguese side are able to welcome back Spanish defender Ivan Marcano.
"I do not think that Franck can play," said Bayern manager Pep Guardiola, who also insisted he would remain at the Bavarian giants next season. "I will speak with our doctor but my feeling is that he can't make it.
"I do not know who will play or who can play. In the past months, I have always decided on my line-up an hour before the game.
Match Details:
Champions League : Bayern Munich Vs FC Porto
Tuesday, 21 April , 2015
Allianz Arena , at 19:45 GMT"Bastian Schweinsteiger has trained again for the first time and the more players I have the better."
Bundesliga champions Bayern remain on course for a second successive German league and cup double, but their ambitions of a treble have been hampered by a poor defensive display in the first leg.
However, forward Thomas Muller remains confident the five-time European champions can overturn the deficit and reach a fourth successive Champions League semi-final.
"I know we are able to do it - a 2-0 win playing at home wouldn't be a historic score. It is doable," said the Germany World Cup winner.
"I don't know exactly how we are going to do it but we will do it."
