The 34-year-old Hungarian has not played for the Baggies since January due to a serious knee problem.
"I have had a tiny teardrop muscle strain so I have reduced my number of training sessions," Gera told his official Facebook page.
"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."
West Brom are currently in 14th place in the Premier League table with five points from their opening five matches.