Arsenal's German playmaker Mesut Ozil will be out for between three and six weeks, manager Arsene Wenger said on Friday.
Ozil, the club's £42 million ($69.8m, €50m) record signing from Real Madrid last summer, suffered a hamstring injury in his side's 1-1 draw at Bayern Munich on Tuesday, which saw Arsenal eliminated from the Champions League 3-1 on aggregate in the round of 16.
"We lose Ozil, who has been injured for Sunday, I don't know how long he will be out but it looks a minimum of three weeks," Wenger said ahead of this weekend's north London derby against Tottenham Hotspur.
"When the minimum is three, (then) the maximum is six. I am not specialist enough to know, it is a grade two hamstring (tear), so let's say four weeks."
Midfielder Aaron Ramsey's return from a thigh injury has been delayed, and England international Jack Wilshere is sidelined with a broken foot.
Sweden international Kim Kallstrom could finally be in contention for his debut after signing on loan from Spartak Moscow with a back injury in January while full-back Nacho Monreal is also available again.
Wenger added: "It is of course a blow, but I am confident we have the quality to deal without him (Ozil). We have many creative players who can take over to produce quality performances."