Today's Ohio State-Michigan game is billed as the first edition of Ryan Day vs. Jim Harbaugh, and it is.

Day is the first-year Buckeyes coach. Harbaugh is the fifth-year Wolverines coach seeking an elusive first victory against Ohio State.

The coaches are acquaintances at most. Day is much closer with Michigan defensive coordinator Don Brown, and the Day vs. Brown battle is more pertinent than the Day vs. Harbaugh one.

Get the news delivered to your inbox: Sign up for our BuckeyeXtra newsletter

A year ago, Day was the offensive coordinator and play-caller for Ohio State when the Buckeyes' offense thrashed Brown's top-ranked defense in a 62-39 OSU win.

That made the offseason a long one for Brown and the Wolverines. Day remains the play-caller for the No. 1 Buckeyes (11-0, 8-0 Big Ten). Will Brown have found the answers for No. 13 Michigan (9-2, 6-2) to slowing an Ohio State offense that no else really has this season?

It will be a chess match based on mutual respect and a long, shared history. Day was the quarterback at New Hampshire almost 20 years ago when Brown was coach at rival Northeastern. Brown later coached Day's brother Tim at UMass. Day and Brown then coached together as Boston College assistants.

“Nothing but respect obviously for his background and what he's done defensively over the years,” Day said. “One of the best guys in the business.”

Brown earned a reputation for innovative, flexible defenses.

“Nobody gives more looks than Don Brown,” Day said.

Brown had every reason to believe that his defense last year would have the answers against Ohio State. Instead, Day's play-calling kept the Wolverines a step behind all day as the Buckeyes used crossing patterns and other routes that got receivers in space.

If anything, Day's challenge last year was easier than it was in his first Michigan game. In 2017, quarterback J.T. Barrett's knee was injured when he was mysteriously hit by a camera before the game. Barrett gutted it out the first half before Dwayne Haskins Jr. had to rally the Buckeyes to victory in the redshirt freshman's first meaningful action.

After 62-39, Day knows that Brown has plotted for 364 days for redemption. But last year provides only clues, not a blueprint.

“This is a whole new year,” Day said. “We look at the film a little bit to see what they did. They're going to make adjustments on all that stuff. We're really looking at this year — what we do, what they're doing. Their personnel is different now. What he's doing is significantly different.”

Ohio State's offense is different, too. The Buckeyes have dropped the shovel pass, a staple under Urban Meyer. They aren't running as many crossing patterns. They are playing to Fields' strengths, which includes his legs, along with a run game that's much better than last year's.

Ohio State leads the country in points per game (49.4) and is sixth in total offense (530.4 yards per game). Michigan's defense doesn't have the stars it had a year ago, but it allows the 10th-fewest points (16.2) in the country and is fourth in yardage allowed per game (267).

Day has gotten the better of Brown the last two years, but to win his debut as coach, he needs to win the chess match with Brown again.

“He puts his guys in positions to be successful,” Day said. “He does a great job. I know he's going to do another good job this weekend.”

brabinowitz@dispatch.com

@brdispatch