The versatile back-five forward has not played since the Ospreys’ comfortable home win over Glasgow at the beginning of March due to a hamstring injury.
It had been hoped that Thomas would have recovered in time to face the Men of Gwent in the crunch Welsh derby but he will once again be forced to sit out for the Magners League Champions.
“He is unlikely to play this weekend,” said Ospreys physio Chris Towers.
“The plan is to review the situation early next week and decide if he is ready for our next match.”
The Ospreys are desperate to get back to winning ways after losing to Edinburgh and drawing with Cardiff Blues in recent weeks.
