Coach Jim Harbaugh said Monday that he didn't know whether the two players would miss all of spring practice. Wide receiver Donovan Peoples-Jones is also not participating. Michigan began spring practice Sunday.
Harbaugh also said running back Zach Charbonnet needed a scope for his meniscus and isn't participating in spring practice. He said quarterback Dylan McCaffrey is back to 100 percent.
Harbaugh added that running back Chris Evans is not with the team, but he left open the possibility of a return. Evans announced in February that he was going through academic issues.
Earlier this offseason, Harbaugh hired Josh Gattis away from Alabama to be his offensive coordinator. Harbaugh said he expects a more up-tempo offense this season and that Gattis will call plays.
"The tempo's a huge change," Harbaugh said. "It's got more of an attacking feel to the offense in terms of tempo and in terms of going downfield in the passing game."
Harbaugh also addressed the departure of defensive line coach Greg Mattison, who went to Ohio State to become a co-defensive coordinator.
"He wanted to be a coordinator again, and darn near doubled his salary. I don't hold that against him. We're not going to be sending each other Christmas cards, based on where he went," Harbaugh said. "Still a good man, still have a ton of respect for him. We'll be friends again someday, when we're done coaching."