The French defender was forced off with about 20 minutes left in the Europa League clash and manager Andre Villas-Boas admits it is a bit of a concern.
"It's a bit of a problem because of his injury in the knee it has taken him time for his body to adapt to new positions on his run," Villas-Boas said.
"Because of that he's putting extra strain on his muscles and keeps getting small contractions that limit him finishing the games.
"At the moment it doesn't look very serious but it will force him to stop for a week or so.
"When we get him back we will give him a one-week or two-week preparation to be physically better."
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