The 25-year-old underwent surgery towards the end of last season, but has been struggling again in the opening weeks of the new campaign.
Os boss Martin Ling told the Epping Forest Guardian: "Tam has been struggling again with his groin, so we sent him for scans.
"They have revealed a slight tear, although the good news is that it isn't related to the operation he has just had.
"We are not sure exactly what has caused this latest problem, but it maybe a case of where he might have been trying to overcompensate in a certain area because of the original injury.
"The bad blow is that he could be out now for between ten days and two weeks, which is a massive loss to us, but hopefully this time we can resolve matters once and for all."