The extent of Theo Walcott’s injury has been revealed…

Arsene Wenger will be without Theo Walcott for three vital games after he was injured against Sheffield Wednesday.

The England forward picked up a calf strain just minutes after coming on as a substitute in Arsenal's 3-0 defeat to the Championship side in the League Cup on Tuesday. According to The Telegraph, Walcott will be out for three weeks - which means he will miss key trips to Swansea and Bayern Munich, and the home match against Tottenham Hotspur. The former Southampton man has impressed since being given a run in the team as a striker, but Arsenal fans will now have to deal with the all too familiar sight of him on the sideline. Swansea have been real bogey team for Wenger recently, as the Swans claimed all six points from the two games between the teams last season. Meanwhile, losses to Dinamo Zagreb and Olympiakos earlier in the tournament give much more importance to the Gunners' trip to Munich as they look to get to their first Champions League quarter-final since the 2009/10 season. Walcott will also be absent for his team's trip to White Hart Lane for the north London derby next month, with Wenger hoping he will return to action after the international break.