Michigan football coach Rich Rodriguez has toed the line between holding physical practices and not getting his players hurt.

As a handful of players sat outside lines during today's practice wearing red jerseys, meaning they were out with an injury, the Wolverines are really beginning to feel the danger of physical practices.

Redshirt junior right guard Cory Zirbel's knee injury may be "long-term," according to Rodriguez.

"We're not even hopeful that he'll be able to return this year," Rodriguez said. "We're just waiting to see how he responds to surgery. When they get in there and do an arthroscopic surgery, they'll have more answers."

Freshman wide receiver Terrance Robinson will be out for several weeks, too.

Robinson being out will likely give more opportunities to slot receivers like freshman Martavious Odoms, sophomore Toney Clemons and freshman Roy Roundtree. And running backs will probably spend more time in the slot, too.

And Zirbel's backup, redshirt freshman Mark Huyge had a high-ankle sprain and is week-to-week.

So redshirt sophomore John Ferrara moved from defensive tackle to right guard after the coaching staff considered the move for the last couple weeks. Rodriguez even said he could be starting by the Aug. 30 opener against Utah.

Offensive line coach Greg Frey had been joking with Ferrara for some time now about the move, and offensive coordinator Calvin Magee had been anxiously awaiting the switch. Finally, Rodriguez asked Ferrara if he wanted to move, and Ferrara said he would do whatever was best for the team.

"John's a natural athlete, and a he's really smart guy, so he can pick up the offense pretty fast," redshirt sophomore right tackle Stephen Schilling said.

Ferrara played tight end in high school but was much more of a pass-catcher than a blocker. But Ferrara has adjusted quickly, beating sophomore Brandon Graham in a one-on-one in practice.

Ferrara said the easiest part about the switch is that he knows all of the defense signals and can call them out for the offense.

"John Ferrara is the enemy now," Taylor said. "He went over to the dark side."

Sophomore cornerback Donovan Warren, who had a cold, also didn't practice today as a precautionary move.

Defensive coordinator Scott Shafer said the decision also gave the coaches a chance to assess other players. Sophomore Troy Woolfolk and freshman Boubacar Cissoko saw more reps.

Injuries depleted Michigan's already thin guard-corps. The Wolverines are thin at tackle, too. If a player or two at that position is injured, could one of Michigan's eight tight ends move there?

"I think those guys know we look for that, so they're all losing weight," Magee said with a laugh.