Michigan football has reached the halfway point of spring practice this year and a pair of lingering injuries have Jim Harbaugh more concerned than he was when camp began.

Donovan Peoples-Jones, Michigan's receptions leader from a year ago, has not been able to practice this spring due to a lingering groin injury. Michael Dwumfour, a starting defensive tackle last year, has been out after suffering a plantar fascia injury late last season. Dwumfour said via Twitter he suffered the injury in a win over Maryland on Oct. 6.

Both injuries, Harbaugh said, could be more serious than the team first thought.

"Donovan Peoples-Jones, Michael Dwumfour. By all indications it looks like they have more serious injuries than we previously thought," Harbaugh said. "Both have not participated in any practice or all winter. The concern is that (it is) more serious (and we'll see) if they can get back to their previous form and level."

Asked if these injuries could linger into the fall and cost either player game time, Harbaugh said it's possible.

Though it'll all be about the recovery process. He said neither injury is expected to require surgery moving forward.

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"I've always been, as a coach and when I played, I put a lot of stock in how a player's body feels. How they respond. That's the feedback. All indications we're getting is that they really can't do much at all," Harbaugh said. "You always hope for the best.

"Donovan has a soft-tissue injury. A groin injury. Michael had a torn plantar fascia right before the bowl game. You start to worry when injuries linger longer than you previously thought. Or longer than the time it usually takes. But nobody knows their body better than the actual person who is out there."

Elsewhere, starting wide receiver Nico Collins — who led the team in receiving yards last season — is progressing well after undergoing an offseason surgical procedure. Harbaugh did not divulge the nature of Collins' injury but also didn't seem to be as concerned as he was with either Peoples-Jones' or Dwumfour's injuries.

With Peoples-Jones and Collins out, Michigan has worked true freshman Mike Sainristil and third-year sophomore Oliver Martin as the starting wide receivers alongside third-year sophomore Tarik Black this spring. Carlo Kemp and Donovan Jeter (nose tackle) have been Michigan's two interior defensive linemen.

Harbaugh also said starting cornerback Lavert Hill has progressed well after an offseason surgery of his own. Harbaugh said it's possible, though not a guarantee, that Hill will be able to get some practices in before the session is over.

Starting inside linebacker Josh Ross has been sidelined in spring ball due to a hamstring injury, though he could be back soon, Harbaugh said. Redshirt freshman Cameron McGrone and third-year sophomore Jordan Anthony have taken his reps as he recovers.

At running back, redshirt freshman Christian Turner had a hamstring injury that flared up early in spring ball that has kept him out. Michigan was already without freshman running back Zach Charbonnet (knee) this spring. Second-year running back Hassan Haskins has also been banged up. With those players slowed, Michigan has slotted senior Tru Wilson as the starting running back with converted linebacker/tight end Ben VanSumeren as the primary backup.

Contact Nick Baumgardner at nbaumgardn@freepress.com. Follow him on Twitter @nickbaumgardner. Read more on the Michigan Wolverines and sign up for our Wolverines newsletter.