"We really felt good yesterday," head coach Doug Marrone said. "Then we had a setback. So it's going to be a day-to-day thing. That's not the best of news."
Marrone wasn't ready to rule out Lawson for Sunday's game in New Orleans, saying that Lawson, as a veteran, may have more leeway on whether he plays after not practicing.
"He's missed two days of practice," Marrone said. "But Manny's smart and he's a veteran guy. So that's why it'll be day-to-day."
Lawson, in his eighth season, has started the first seven games, recording 40 tackles, a sack, and a forced fumble.
The following is the Bills' full Thursday injury report:
DID NOT PRACTICE
QB EJ Manuel (knee)
LB Manny Lawson (hamstring)
RB C.J. Spiller (ankle)
RB Fred Jackson (knee)
DT Kyle Williams (Achilles)