Greg Mattison is set to retire at the end of January after two seasons as the Buckeyes' co-defensive coordinator, Ryan Day announced on Friday.

“He’s going to be retiring here after an unbelievable career at the end of the month,” Day said during his first press conference since the national championship game. “He’s a special guy. He and Ann, his wife, have been so gracious to Nina and I in helping us in our first two years as head coach. His career speaks to itself. What he’s done and accomplished on the field but more importantly, it’s what he’s done off the field. The relationship and respect he has around the country as one of the best coaches, and the impact he’s had on so many people.

“So I can’t thank him enough. I know he’s gonna really miss it, but he’s gonna have an opportunity to spend some time with his grandkids and his children after an unbelievable career in coaching football.”

Mattison joined the Buckeyes in 2019, leaving Michigan to cross rivalry lines, when Ryan Day took over as head coach and revamped the defensive coaching staff. He served as co-defensive coordinator for both of his seasons on staff, pairing with Jeff Hafley in 2019 and Kerry Coombs in 2020, while also coaching the Sam linebacker position.

His decision to retire, at 71 years old, comes after 49 years in coaching, starting as a high school head coach and including a stint with the NFL's Baltimore Ravens along with more than 40 years as a collegiate assistant.

Now, Day will have to determine how to most effectively replace Mattison on staff – a move that could be important given the Buckeyes' defensive struggles, specifically on pass defense, this past season.

Day said Ohio State is working to find a replacement, but acknowledged that Mattison “will not be an easy guy to replace.”

“We’re working on replacing Greg,” Day said. “It will not be easy. But we’re gonna get to work on that here.”

While Coombs was already the primary defensive coordinator this past season, questions remain about his ability to lead the defense on his own after the 2020 Buckeyes failed to pick up where Hafley left off, which could make it important for Mattison's replacement to be another co-defensive coordinator who could make improvements to the defensive scheme.

Given that the Buckeyes already have a defensive play caller in Coombs and a linebackers coach in Al Washington, Day doesn't necessarily need to hire someone to fill the same exact role Mattison did. Coombs could be the sole defensive coordinator going forward, and Washington could be the sole linebackers coach.

After a disappointing first year for the defense under Coombs' leadership, though, this could be an opportunity for Day to shake things up as he deems necessary to get Ohio State's defense back to its elite standard.

Day said Friday that a decision had not yet been made whether Ohio State would hire someone to fill the exact same role as Mattison or whether returning defensive coaches could be moved into different roles.

While Mattison's only position coaching responsibility was the Sam linebackers and he was not one of Ohio State's more active recruiters, Day said his veteran mentorship played a crucial role in the Buckeyes' success over the past two seasons and that Mattison's presence will be missed inside the Woody Hayes Athletic Center.

“If you ask Justin Hilliard and Pete Werner and all those linebackers that he spent so much time with this year and last year, the relationships that he built here, I think they’d talk for awhile about what he meant to them and their development,” Day said. “He was just a steady force, and just a calming force with a ton of experience, and just meant so much to everybody in that room. I think he deserves a lot of credit for that. Somebody that I leaned on just for advice with all his experience. Unbelievable person, he and Ann mean so much to us, so again, he had his impact these past couple of years. They’ve been successful. Only lost two games. And a lot of that has to do with Greg.”