EAST LANSING, Mich. — Mark Dantonio’s phone rang early Sunday morning. He was busy changing a diaper.

When he hung up with Michigan State athletic director Alan Haller, Dantonio himself changed — from affable “Grandpa Mark” back into football-focused “Coach D.”

Dantonio quickly returned to campus Monday to become Michigan State football’s associate head coach, getting up to speed on what help his protégé Harlon Barnett as acting head coach.

“Well, I think that every day is a new day,” Dantonio said late Friday afternoon at MSU’s Clara Bell Smith Center. “To me, great challenges bring on great adversity, which provide great growth for people. And so for coach Barnett and our football team, it’s another lesson in life.

“As I said when I walked out of here, there’s there is nothing that won’t be changed inevitably. So change is inevitable for all of us. It’s a tough situation.”

Former Michigan State football coach Mark Dantonio, right, and MSU Athletic Director Alan Haller mingle on the field before the football game against Central Michigan on Friday, Sept. 1, 2023, at Spartan Stadium in East Lansing.

Barnett takes over following Mel Tucker’s suspension by Haller on Sunday following a USA TODAY story that detailed allegations of sexual impropriety for the fourth-year head coach’s actions on a phone call with sexual assault victims advocate Brenda Tracy. Tucker was hired eight days after Dantonio’s abrupt retirement in early February 2020.

“I told him, I said, ‘I’m thinking about doing this.’ And then he said, ‘How about this?’” Barnett said Tuesday about Dantonio. “I can’t share all this stuff and I don’t really want to share all of it. But he’s I’m glad he’s here. Love me some Coach D, man.”

Dantonio’s final game as MSU’s coach was the Pinstripe Bowl in New York on Dec. 30,…