David Moosman joked it was nice while it lasted. His shift back from center to guard lasted less than a quarter.

Then the guard-turned-center-turned-guard again watched as starting center David Molk, who had missed the past four games with a foot injury, crumpled to the ground with a torn right ACL.

Molk’s season is done. He'll miss spring practice, too. And Michigan’s offensive output became more fragile with the tear of a tendon.

“Those were five good plays,” Moosman said. “But it’s tough to see Molk get hurt, but whatever I need to do.”

In Molk, Michigan loses its best offensive lineman and perhaps its best offensive player, period.

The center often is the second-most critical player on an offense besides the quarterback. He is responsible for all the decisions made by the offensive line and in some cases, audible checks and calling out the middle linebacker.

More importantly, the center is often the traffic controller and without him, an offense can look lost.

Which, in many cases, you can say about Michigan without Molk.

Michigan had its best rushing game of the season - Delaware State doesn’t count - with Molk in the lineup, gaining 380 yards against Eastern Michigan. It also had its best passing game, 240 yards against Notre Dame, with Molk.

Since he left, Michigan has yet to run for 200 yards against a Football Bowl Subdivision opponent and has thrown for over 200 yards just twice.

It has also broken 300 yards of total offense in just two of the four FBS games since Molk’s injury.

No Michigan rusher has had a 100-yard rushing game against a FBS school, either. Since Molk’s foot injury, Michigan’s quarterbacks have been sacked 11 times.

Combine it with running back Brandon Minor’s continuously murky health status and, well, it doesn’t bode well for the Wolverines.

“(Molk’s) an outstanding player and there’s no question with he and Minor both, you’re talking about two of our best offensive players,” Michigan coach Rich Rodriguez said. “These guys know whoever the next guy is you put them in that spot and you move forward.

“I would like to sit here and tell you our depth is so good that you lose one or two guys and it doesn’t have any impact. But any coach will tell you if you have any great players and you lose them to injury, it’ll have an impact.”

Judging from the games Molk missed earlier in the season, his injury will absolutely have an impact on the Wolverines.

Moosman struggled snapping the ball against Indiana, sending balls flying past both quarterbacks, Tate Forcier and Denard Robinson. They also struggled blocking opposing defenses.

Granted, the talent level of the teams Michigan played increased, especially defensively playing Iowa and Penn State, but still, the Wolverines looked less than comfortable.

That was obvious after Molk’s injury when, in the second quarter against the Nittany Lions, the offensive line had a holding call that was declined, a false start and a snap out of the end zone resulting in a safety. All in one series.

“I think I screwed up just about everything you can at center, so hopefully I can’t do that again,” Moosman said of his first run at center. “I’ve gotten all the bad stuff out of the way and only good things forward.”

Moving forward, Moosman said he needs to calm down, that center is a position more of responsibility. And that’s something he’s still getting used to.

But he’ll be the man in Michigan’s middle for the end of the year.

So with Molk done, he’s got to figure it out.

“You need to bring it together and can’t get amped up by everything,” Moosman said. “You have to be calm and collected.”

The injury does more than hurt Michigan. It hurts Molk. Because he played against Penn State, he will be unable to claim a medical redshirt since he played after the fourth game of the season. He also suffered his second major injury of 2009, although this one is more serious than his foot problems. There’s also the risk of, with two injuries in a year, of Molk being labeled injury-prone by NFL scouts.

And Molk, a sophomore, certainly has an NFL future.

But the immediate concern is for Michigan’s offense - a unit that needs to find a way to move on and block well without him.

Michael Rothstein covers University of Michigan sports for AnnArbor.com. He can be reached at (734) 623-2558, by e-mail at michaelrothstein@annarbor.com or follow along on Twitter @mikerothstein.