Wenger said he was worried about an injury that will keep Walcott out of Saturday's match at Newcastle United and makes him a doubt for England's upcoming friendly against Slovakia and World Cup qualifier against Ukraine.
"We are surprised and worried," Wenger said on Arsenal's website. "He was in very good form coming back and that is very bad news for us and for England.
"For the rest of the season might be too long, but he's out of tomorrow's squad and he could be out of the England squad."
The extent of the 20-year-old winger's injury is not yet clear but Wenger told reporters it could be a cartilage problem.
"We have to see how he responds today and I hope it's not really serious," Wenger said.
ARSENAL FANS! Check FourFourTwo.com’s ever-expanding interviews archive for more stuff to read:
Web Exclusives Patrick Vieira, Cesc Fabregas
Q&A Theo Walcott, Cesc Fabregas
One on One Arsene Wenger, Thierry Henry, Ian Wright
Boy's A Bit Special Theo Walcott, Armand Traore
Perfect XI Ian Wright
What Happened Next? Gus Caesar, Peter Marinello
And Another Thing Being a Big Four fan
