TEMPE, Ariz. -- How Rashard Mendenhall's toe feels Sunday morning will determine what the Arizona Cardinals' running back corps will look like against the Atlanta Falcons at University of Phoenix Stadium.

Mendenhall, who didn't practice at all this week because of lingering turf toe, was listed as doubtful on Friday's injury report. If he can't play Sunday, rookie Andre Ellington will get the start, Arizona coach Bruce Arians said. Fellow rookie Stepfan Taylor will be the Cardinals' second option at running back.

Arians has said all season that Ellington isn't big enough to shoulder a full-time load at running back, and the coach won't treat Sunday any differently if the Clemson product starts.

"I look at him the same way and it's still situational," Arians said. "We'll monitor how many times he carries it."

Ellington says he's capable of carrying the ball for a full game. In the past two games, Ellington has played more snaps than Mendenhall, but Mendenhall has been Arizona's primary option running the ball.

Through seven games, Mendenhall has 92 carries for 281 yards, a 3.1 yards-per-carry average. Ellington, however, has 179 yards on 28 carries, a 6.4 yards-per-carry average.

But the numbers don't mean anything to Ellington. He wants the ball all game.

"Until the clock says zero in the fourth quarter," he said. "I don't have a set number. I just go out there and play ball. If you start thinking about those things, then you limit your skills."

If Mendenhall can't play, the Cardinals would be left with three running backs unless Ryan Williams is activated for the first time this season. That will be a game-time decision, Arians said, based on who else is injured.

Arians has said Williams' lack of special teams experience hurts his chance to get on the field, but the running back said that's easily correctable.

"I believe that special teams is an effort phase and I do believe a lot of people can play special teams, all you have to do is put forth the effort and get the scheme down right," Williams said. "But if that's what's keeping me off the field, then I guess that's what's keeping me off the field. Man. I don't know, man.

"I have no answers for anything. I don't know. I don't know what’s going to happen this Sunday or anything of that sort. I didn't even know if it was going to be a GTD [game-time decision]."

Williams continues to work through his reps at practice, preparing as if he'll play every week. He hasn't heard yet if there's a chance he'll be activated for Sunday, and he hasn't talked to Arians about it.

But Williams know his legs and body have benefited from not playing through seven games.

"I'm probably the freshest guy on the team right now," Williams said. "I'm ready to play. I'm just waiting. It's a waiting game right now."