Neither player practiced this week, and their status for Week 5 is uncertain. McCoy said in the Bills locker room Friday that he won't play until he feels fully healthy.
"One thing I just promised myself is that I can't go out there if I'm not 100 percent," McCoy said. "So if it's this game or the next game -- whatever it is -- I'm rushing to get back, but I'm not playing until I'm 100 percent."
"To be honest, actually right after that game, I was just getting better, feeling better. And I think that Thursday, I kind of hurt it again. And that's where it went wrong," he said. "I tried to really push it. I guess I messed something up."
McCoy was limited to 16 yards on 11 carries against the Dolphins.
"It's acceleration," McCoy said. "Certain plays I can't get to 100 percent or full speed. Usually where I can kind of accelerate through and burst through, I don't have the same type of get-up.
"I'm not the bruising type to be just running through everybody. My thing is just making them miss and getting out of there. If you can't do that, you can't do nothing."
Rookie Karlos Williams will start for McCoy at running back. A fifth-round pick from Florida State, Williams rushed for 110 yards in Sunday's win over the Dolphins, the fourth-most rushing yards by a Bills rookie in the past 20 seasons behind Marshawn Lynch (153 yards in November 2007), Antowain Smith (129 yards, September 1997) and Travis Henry (113 yards, October 2001).
This will be the first time Watkins, who dealt with several injuries as a rookie last season, has missed a regular-season game. The Bills will lean on receivers Percy Harvin, Robert Woods and Chris Hogan in his place.