Arsenal manager Arsene Wenger admits he is unsure when Theo Walcott will be available again after picking up an injury in Sunday's warm-up.
Walcott was in the starting line-up for the match against Stoke yesterday, but withdrew before kick-off after injuring himself in the warm-up.
Wenger told reporters: "We hope we haven't lost Walcott for a long time."
"He had an abdominal muscle problem, I don't really know what it is."
"Nobody can tell me whether it is just a question of days."
"He had a test before the game and I decided to play him but he had a little problem before the Marseille game (last week) and it then became a bit worse."
"It's a bit mysterious, because we don't really know what it is."
Walcott adds to Wenger's injury woes this season, with Santi Cazorla (ankle), Yaya Sanogo (back), Tomas Rosicky (hamstring), Lukas Podolski (hamstring), Alex Oxlade-Chamberlain (knee) and Abou Diaby (knee) already on the list of absentees.
Some good news for Gunners fans, Mikel Arteta returned from a spell on the sidelines yesterday, completing the last 10 minutes against Stoke.
Wenger hopes to have other key absentees back in the first-team after the next international break in October.
Arsenal face West Brom in the League Cup on Wednesday, and it is thought that Wenger will use that game as a chance to rest some key players.
"I have to rotate [for the West Brom game] because we have many players on the fringe and I have to make some decisions," he said.
"We have a game on Saturday and a game against Napoli [in the Champions League] after that so we will have to rotate."
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