A defense that surrendered a school-record 28.9 points per game last season and returned just four starters to their positions isn’t supposed to look stunning in its home opener.

It shouldn’t hold a highly touted senior quarterback and potential NFL draftee to 13-for-24 passing and 81 yards in the first half.

And it certainly doesn’t come within nine minutes of its first shutout in the Rich Rod era.

“If anybody’s surprised, it’s y’all,” junior safety Troy Woolfolk said after the Michigan football team’s 31-7 win over Western Michigan. “I knew we were all playing for this team, and I knew this defense was going to be good.”

Criticisms of inexperience and lack of depth have surrounded the defense for months. But Saturday, in front of 109,019, the debut of first-year coordinator Greg Robinson’s new defense put at least some of those concerns at bay.

The one glaring concern is that the Wolverines are just an injury away from major defensive problems, particularly in the secondary. That was made clear by redshirt freshman cornerback J.T. Floyd’s botched coverage in the fourth quarter, leading to a 73-yard touchdown pass from Bronco quarterback Tim Hiller.

But the starting corps slowly erased memories of last season's defensive debacle by holding Western Michigan to 3-and-outs on six of eight drives in the first half.

“I just think that we're young and we're learning how to play together in a system that they haven't played in before,” Robinson said of the defense. “There's a learning curve. And I think the guys are doing a pretty good job of adapting.”

The cornerback tandem of junior Donovan Warren and sophomore Boubacar Cissoko held the Broncos’ receivers in check with on-point tackling, and Cissoko delivered with a first-quarter interception that left Robinson jumping ecstatically on the sidelines. The duo helped break apart an Bronco offense which was the nation's 11th-best passing team last year.

Senior defensive end Brandon Graham said this is one of the fastest defenses in which he has ever played.

“Everybody is trying as hard as they can to get to the ball,” Graham said. “And being a shutdown defense, that's what we're trying to do.”

The Wolverines looked like a sure-tackling team Saturday, allowing the Broncos to cross midfield only once in the first half.

Robinson’s main emphasis in his nine-month tenure has been on open-field tackling, which secondary coach Tony Gibson referred to as “probably the hardest thing to do in football.”

“If we’re able to break down and they try to give us a quick move and we’re still able to get in front of them and still shut them down, that’s whenever you know you’re doing the things right that Coach Robinson is telling us to do,” senior outside linebacker Stevie Brown said during fall camp.

Brown, who had started 13 games at safety in his career, switched to a hybrid outside linebacker/safety position under Robinson’s defense. On Saturday, Brown looked fluid in his new position, used his speed to find optimal positioning and finished with five solo tackles.

“I was a little nervous at first because I've been playing against my guys all the time, but now to play against someone different — after the flow of the game, it got very comfortable for me, very natural for me,” Brown said. “It's a good move.”

The Wolverines' biggest defensive test yet will come next week against Notre Dame’s highly touted receivers, namely Golden Tate, who caught 58 passes for 1,080 yards last season.

Did the coaching staff save anything for the Fighting Irish?

“Maybe so,” redshirt junior linebacker Obi Ezeh said with a smile. “We got a lot of stuff.”