Michigan football coach Rich Rodriguez left Saturday’s scrimmage at Michigan Stadium concerned about defense.

Specifically, he’s eager to correct problems defenders have tackling before Michigan opens the season Sept. 4 with a home game against UConn.

"These guys are so strong and talented that you just can't do tackling for 45 minutes a day because you're just so afraid of getting hurt," Rodriguez said Sunday at Michigan's annual media day. "But we've got to work do some fundamental work and balance that with fundamental work versus banging each other up. And we'll do that the next couple of days."

Rodriguez said some of the tackling problems in Saturday's scrimmage point to inexperience - especially in the secondary where veterans like senior safety James Rogers and sophomore cornerback J.T. Floyd have to bring youngsters such as Cullen Christian, Teric Johnson and Carvin Johnson along. And Troy Woolfolk, expected to be a leader in the secondary, went down with a lower-body injury in practice last week.

Michigan secondary coach Tony Gibson singled out safety Cam Gordon as the day's biggest offender, missing five tackles.

Gibson said Gordon was in position to make plays in each situation, but failed to do little things - like not ducking his head and wrapping his arms around the ball carrier. Rodriguez said Gordon "didn't have the best day" and that "if you make a mistake back there, it's six points."

Michigan defensive coordinator Greg Robinson said Sunday he believes the Wolverines' tackling issues are correctable. Without naming names, Robinson said some players are in position to make plays, but just don't carry out their jobs.

"Some of them are better at it than others, but you never quit working on those things," Robinson said. "It's getting in position, being in control and being aggressive and going and doing it. There are a lot of elements that go into tackling and if you tackle our offense well, you're a good tackling football team because you're facing some very good athletes.

"It's about a team tackling concept that you have to have enough people that even if you miss a tackle, it's minimized because others are there are to compensate."

Rodriguez said the next two weeks should be easier mentally because much of the team's defensive schemes have been installed. The only thing that will be added are small wrinkles to prepare for UConn.

No timetable for Troy Woolfolk Rodriguez said Woolfolk hasn't undergone surgery for the injury he suffered last week in practice. No timetable has been set for Woolfolk's return, but Rodriguez said Sunday "there's nothing that makes us think that he's not going to be able to play again at some point. Troy is as tough as an individual as you're ever going to find. So he'll bounce back."

Plenty of competition on the offensive line Like many other positions, starting spots on the offensive line remain up for grabs. Rodriguez said he likes the way veteran tackles Perry Dorrestein and Mark Huyge have responded to being challenged by youngsters Taylor Lewan and Michael Schofield. While the two redshirt freshmen have gotten bigger (6-8, 294 and 6-7, 293, respectively) and have proven to be able to hold their own on the line, Dorrestein and Huyge have had their best camps since Rodriguez arrived in 2008.

Freshman Jibreel Black impresses Rodriguez Freshman defensive end Jibreel Black has the best chance among Michigan's newcomers to see time up front. The 6-foot-2, 258-pound end isn't quite ready for prime time, Rodriguez said, "but he's shown us enough" that he may not be redshirted when it comes time for such decisions to be made.

"He's a very active guy," Rodriguez said of Black. "He's got a great get-off, he wears No. 55 and he looks a little like (Brandon Graham) at times, but he's not that strong and explosive. He's got a natural burst and some natural ability to him."

Jeff Arnold covers sports for AnnArbor.com and can be reached at (734) 623-2554 or by email at jeffarnold@annarbor.com. Follow him on Twitter @jeffreyparnold.