Bills head coach Rex Ryan did not rule out Watkins playing in Sunday's game against the Tennessee Titans.
Ryan also confirmed Wednesday that Boobie Dixon will serve as the Bills' top running back if neither McCoy nor Williams can play Sunday.
"We'll see. I think Boobie can be a good back," Ryan said. "I think he is a good back, and he's also a good special-teams player. But we'll see. We'll see how Karlos -- he's in the concussion protocol. And we'll see about LeSean as the week progresses. Those two will be out today, but hopefully we can get a shot at one of those guys, too."
"[Herron] has been in a similar system to what we run here with Indianapolis," Ryan said. "Obviously [Colts offensive coordinator] Pep Hamilton and [Bills offensive coordinator] Greg Roman coached together [at Stanford]. So I think some of the terminology is the same. And that's good, because we very well may need him to play this week."