Arsenal face an anxious wait to find out the extent of the hamstring injury to winger Alex Oxlade-Chamberlain.
The 21-year-old, who pulled up during Monday's 2-1 FA Cup win at Manchester United, was having a scan on Wednesday.
His results will not be clear until later in the week, but Oxlade-Chamberlain is unlikely to face West Ham in the Premier League on Saturday.
There is also doubt whether he will be fit for England's qualifier with Lithuania on 27 March.
England face a friendly against Italy four days after the Euro 2016 qualifier.
Wenger told the Arsenal website: "Chamberlain has a hamstring strain. The only thing we don't know is how bad it is, because usually the scans are only done 48 hours after the accident.
"That will be done on Wednesday."
Oxlade-Chamberlain, who had only just returned to the side following a groin problem, could also miss the second leg of Arsenal's Champions League tie against Monaco next Tuesday. Wenger's side trail their French opponents 3-1.
In the Premier League, the Gunners travel to Newcastle on 21 March before they face top-four rivals Liverpool on 4 April following the international break.