The 29-year-old Czech Republic playmaker has suffered a catalogue of injury problems during his time with the Gunners - having joined in the summer of 2006 from Borussia Dortmund - but had enjoyed a run of games in the first team this season.
- Arsenal 2-0 Stoke City: As it happened
However, he lasted only until half-time against the Potters and now faces another spell on the sidelines.
Wenger admitted: "He's devastated and I am as well.
"Before the match I told myself 'he has played the whole game on Wednesday, should I take the gamble or not as it was such an important game?'. But by half-time he was struggling.
"It's a vicious circle when you have been out for a long time. Eduardo had not played for 18 months, Tomas has not played for 18 months.
"When you come back, one or two games, your body has to get used to producing the energy levels again and it's difficult. Nobody masters that.
"The first impression for me is that it won't be longer than a month, but it's a groin problem so we have to see the scan in 48 hours which grade it is - grade one is ten days, but grade three is three."
Source: DSG
