Lyon winger Sidney Govou is facing a spell on the sidelines after limping off with an ankle injury during his side's Champions League match against Bayern Munich.
The France international came off worse in a collision with Bayern centre-back Lucio and was replaced by Ederson in the 36th minute of Tuesday's game.
"Sidney has twisted his ankle, he felt it go," said Lyon coach Claude Puel.
Govou should undergo tests on Wednesday to discover the exact nature of his injury and how long he will be out for.
Puel has a like-for-like replacement for Govou in Kader Keita, who has just returned to action after being out with an arm injury for the past month.
Lyon have picked only one point from each of their first two Champions League outings, now target victory in their next two Group F games, both against Steaua Bucharest.
"We need six points against Steaua to put ourselves in a good position," defender Mathieu Bodmer told reporters after Tuesday's 1-1 draw at Bayern Munich, which followed a 2-2 home draw with Fiorentina in Lyon's first match two weeks earlier.
"To do that we need to play the full 90 minutes the way we played in the first half against Bayern," Bodmer added.
"We had come to win and in the end a point is the absolute minimum we could hope for," said Lyon coach Claude Puel. "We moved ahead and then Karim wasted a match point."
Lyon, desperate to make an impact in Europe at last after never moving past the Champions League quarter-finals, lie second in the group, two points behind Bayern.
"We were too passive in the second half," said Bodmer. "It's a pity because if we had put them under a bit more pressure, we would have had a chance to win it."