The 22-year-old picked up a knock in the win over Bolton and is apparently unlikely to feature against Tottenham at the weekend, with doubts over his availability for Englandhere.
Theo Walcott is set to miss Arsenal's next two matches against Olympiakos and Tottenham, according to The Express.
Walcott picked up a knee injury on Saturday in the Gunners' 3-0 win over Bolton, and appears unlikely to be fit in time to play Tottenham in the north London derby on Sunday.
The news follows reports that Jack Wilshere is set to miss the next five months after surgery on his ankle. The club have announced via their official website that he has undergone successful treatment, but added that he is likely to undergo a prolonged period of rehabilitation.
Arsenal sources have maintained that Walcott’s injury is far less substantial, but with England’s final Euro 2012 qualifier against Montenegro approaching next weekend, it will be a struggle for the 22-year-old to reserve a spot in Fabio Capello’s side.
Andrey Arshavin is likely to replace the winger in Wednesday’s Champions League game as Arsenal look to build on their cagey start to the season, with manager Arsene Wenger hoping to celebrate 15 years as manager of the north London club with a win.