Longtime Michigan football assistant coach Greg Mattison is headed to the team's most hated rival.
According to two sources with knowledge of the situation, Mattison _ who has been head coach Jim Harbaugh's defensive line coach at Michigan since 2015 and on staff with the Wolverines since 2011 _ will join head coach Ryan Day's staff at Ohio State.
Ohio State confirmed the move later in the afternoon, announcing Mattison as a co-defensive coordinator with new hire Jeff Hafley. Mattison's position duties are unclear, as the Buckeyes have also retained defensive line coach Larry Johnson.
Ohio State is not retaining defensive coordinator Greg Schiano.
"Greg is a terrific coach," Day said in a released statement. "His experience as a coordinator and his knowledge of the Big Ten is extremely important to me."
A Michigan spokesman did not immediately respond to a request for comment.
But it seems like a sizable blow to Michigan's coaching staff, as Harbaugh has lost another assistant coach _ one of the most loyal Michigan has had over the past decade _ and this time to the program's biggest foe.
Mattison will become the 11th assistant coach to leave Harbaugh's program since the head coach took over in 2015.
Mattison was in his second stint with the program, as he was originally a defensive assistant with the Wolverines from 1992-96. Brady Hoke brought Mattison back to Michigan in 2011, after he had served as an assistant with John Harbaugh and the Baltimore Ravens.
Under Hoke, Mattison served as the program's defensive coordinator from 2011-14. He was retained by Harbaugh as the program's defensive line coach. He ultimately served as an interim defensive coordinator for Michigan's Citrus Bowl game to close the 2015 season.
The Wolverines then hired defensive coordinator Don Brown prior to the start of the 2016 campaign.
Mattison was in the final year of his most recent two-year deal with Michigan. He made $525,000 last season. His deal was set to expire Thursday. Mattison's deal with Hoke's staff paid him $725,000 annually as the program's defensive coordinator.
Mattison, 69, was known as the top recruiter on Hoke's staff during the first half of his most recent stint, and his defensive lines under Harbaugh produced plenty of talent.
Michigan has had five defensive linemen drafted since 2016 _ Ryan Glasgow, Taco Charlton, Chris Wormley, Maurice Hurst and Willie Henry _ and Mattison was instrumental in recruiting and developing all of them.
The Wolverines are also expected to see former defensive end Rashan Gary get drafted in the first round of the upcoming 2019 NFL draft. Mattison was a key part of that recruitment as well. Chase Winovich, another Mattison project, is also expected to be drafted.
In terms of his ties with Ohio State, Mattison has been a long-time friend of now former Buckeye head coach Urban Meyer. He worked on Meyer's Florida staff from 2005-07, helping the Gators win a national title in 2006.
Day was a graduate assistant on that Florida staff in 2005.
Mattison's departure comes roughly two weeks after Harbaugh told reporters after a disappointing Peach Bowl loss he didn't anticipate any further coaching turnover this offseason.
"I think we're going to take what we have and reload. A new season and tighten up," Harbaugh said. "But keep working. Keep working to put it over the top."
Mattison is the second staff departure from the 2018 staff. Wide receivers coach Jim McElwain left to become Central Michigan's head coach prior to the bowl game in December.
