The England star suffered an injury to his buttock muscles in Arsenal's 3-3 home draw.
Walcott - hoping for a spot up front in Wednesday's friendly in Sweden - will need to be assessed before seeing whether he can join up with Roy Hodgson's England squad.
Gunners boss Arsene Wenger said: "Walcott has a glute muscle problem. We nearly took him off at half-time, he nearly went down, but we left him on and on.
"In the end, it got worse and worse. At the moment, he is limping so I do not know whether he will be able to join the national team or not."