Robert Lewandowski is working on returning from a broken jaw, broken nose and concussion suffered in last week's match against Borussia Dortmund.

Bayern Munich said last week they were "profoundly convinced" that Lewandowski would be available for the first leg of their semifinal at Barca on Wednesday, and the striker used his Twitter account on Sunday to say he was "ready for the next challenge."

Lewandowski missed training on Sunday, and Bayern sporting director Matthias Sammer has said he will only play at the Camp Nou if he is fully fit.

"The doctors will decide it, along with the player himself and also [how he feels when wearing] the mask, but one thing's for sure -- no player in the world can be so important that you'd put his health at stake," Sammer told reporters after the Leverkusen defeat."

Lewandowski returned to training on Monday.