ANN ARBOR, Mich. (AP) -- The optimism surrounding the Michigan basketball team this season is predicated on one main thing -- better health for the team's top players.

Coach John Beilein says swingman Zak Irvin should at least be back on the practice court by the start of the season. The school announced Sept. 9 that Irvin was having back surgery and would miss 6-to-8 weeks. The Wolverines open the season Nov. 13 against Northern Michigan.

Friday was the first official day of practice for Michigan. Caris LeVert, Derrick Walton and Spike Albrecht, all of whom are returning from injuries, were able to participate. Irvin couldn't participate fully.

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"I anticipate him to be on the court either in practice or in games by the start of the season," Beilein said.

LeVert did not play after Jan. 17 because of a foot injury, and Walton was out after Jan. 24 with a lingering toe problem. Albrecht had hip surgery in the offseason.

"The two that I think are at 100 percent right now are Derrick and Caris," Beilein said. "We're trying to just rotate Spike out of drills, but there's really no restrictions other than he's not moving the way he'll be moving in a couple more weeks."

The 5-foot-11 Albrecht and 6-7 LeVert are seniors, and having two key players with so much experience is a rarity at Michigan, which has lost several stars early to the NBA in recent years. Irvin and Walton are juniors.

If all four are at full strength, the Wolverines should be much improved after going 16-16 last season.

Irvin led the Wolverines in points (456) and minutes (1,160) last season. LeVert led Michigan in scoring average at 14.9 points per game.

Michigan began Friday with a 6:30 a.m. walkthrough, then opened practice to media in the afternoon. Beilein said the early walkthrough is not something he's typically done before.

"It was dummying things before we watched it on film," Beilein said. "We're going to do more of it this year, more attention to certain details of the game so that when we do practice later that day or later on, we don't have to stop practice."

The early start took Walton by surprise.

"When I first heard, I was kind of shocked," Walton said. "I thought it was kind of a typo on the calendar. It was different. He just kind of gave a rundown on how practice will flow and the new things we're going to do. It's kind of like a warmup practice."