Vikings coach Leslie Frazier doesn't expect injured running backs Adrian Peterson and Toby Gerhart to practice until Friday, if at all this week, but hasn't ruled either player out of Sunday's game against the Eagles at Mall of America Field.

Frazier said he's more optimistic that Gerhart (hamstring) will return Friday but added that Peterson (mid-foot sprain) "is a fast healer, as we all know."

"He can do things that most can't when it comes to coming back from injury," Frazier added. "He believes he's going to be ready to go. We were walking up the stairs a few minutes ago and I said, 'Hey, what do you think?' And he said, 'I'll be ready, Coach. Don't worry about me.' That's Adrian. So we'll see."

With torn ligaments and a Lisfranc injury ruled out by a series of tests Monday, Peterson's ability to play will come down to "pain tolerance and [whether he can] do some of the things he needs to do to be able to protect himself," Frazier said. But Frazier also said the team will proceed on the side of caution, keeping in mind Peterson's long-term value and the fact the Vikings (3-9-1) are eliminated from playoff contention.

Peterson did some exercises in the pool Wednesday and will do so again Thursday. If he's not able to practice Friday, Frazier said he won't play Sunday.

The Vikings added to their running back depth by signing Bradley Randle, a rookie from Nevada-Las Vegas, to their practice squad Wednesday. They also have Joe Banyard on their practice squad. Both players were with them in training camp. If Peterson and Gerhart can't play, Banyard or Randle would be promoted to back up Matt Asiata.

Dml - Mckenna Ewen Special To The Star Tribune, Star Tribune
Vikings running back Adrian Peterson was carted off the field after injuring his ankle in the second quarter.

Floyd's 'exponential' growth

Rookie defensive tackle Sharrif Floyd has been more noticeable the past two weeks with seven tackles, three for losses, one sack and three quarterback hits.

"He's maturing as a young player, and part of that is being around a Kevin Williams and a Jared [Allen] and those guys and watching how they do things in practice," Frazier said. "But his growth over the last, say, two or three weeks has been exponential. He's really come along."

Frazier's future

Some players were being asked in the locker room Wednesday to speculate about Frazier's future. Linebacker Chad Greenway and receiver Greg Jennings complimented Frazier for how hard the team has continued to play despite four last-minute losses and another blown fourth-quarter lead that led to a tie.

"He's definitely been holding things together," Jennings said. "As far as the future, I don't know. Just like from a player's standpoint, we don't know. We don't control that. That all goes from upstairs, down."

QB differences

While comparing the similarities of quarterbacks Matt Cassel and Christian Ponder, Jennings had an interesting take on what he considers their main difference.

"The way they approach the game is pretty much similar," Jennings said. "They both study, they're both very smart quarterbacks. Honestly, they both give us a chance to win.

"I think the number one difference is just the experience. Matt, you can feel that he's much more experienced. He's a lot freer out there. When Christian's out there, he's free, but he's not as free as he may possibly want to be."

Asked to elaborate on what he means by "free," Jennings said: "Just playing loose and not tight and trusting everything. Trusting himself, trusting the guys around him, just being free and having fun playing football."

Etc.

• Josh Freeman will be the No. 3 quarterback for the sixth time in nine games since being signed Oct. 6.

• Tight end John Carlson, whose history of concussions continued Sunday with his second in two years with the Vikings, won't return to practice until he's passed the league-mandated concussion protocol.