The Hungary international was ruled out of Wednesday's Capital One Cup tie against Arsenal, and Gera took to his Facebook page to explain the situation.
The injury is a setback for the midfielder in his recovery from a serious knee ligament problem sustained in January during the FA Cup third round tie against QPR.
Whilst there had been suggestions he could return for Wednesday's game, the Premier League tie against the same opponents on October 6th could be a more realistic return date.
"I got many anxious messages after it was published on the WBA website that I wouldn't play against Arsenal," Gera wrote on his official Facebook page.
"There is no serious problem, but it is true that I won't be involved tonight.
"I have had a tiny teardrop muscle strain so I have reduced my number of training sessions. I'm not happy with it but the doctors have said it was expected because of the hard training I've done in the last few weeks.
"Doctors say I may be able to play matches within a fortnight."