Per the Official Site:
Thomas underwent an MRI on Tuesday, and the results confirmed that there was a tear.
As to Thomas's availability for the remainder of the season, Gibbs said: "We're just going to have to evaluate after the surgery what we think would be the time frame for him coming back."
It's likely that Thomas will be sidelined for a significant period of time.
If it's determined that Thomas could return post-surgery by November or December, then the team could opt to keep him on the active roster so he is available for the stretch run.