History was on Ohio State's side coming into its rivalry game against No. 5 Michigan on Saturday. The No. 2 Buckeyes had won 15 of the past 16 iterations of The Game, including eight straight dating back to Nov. 26, 2011. Ohio State coach Ryan Day had been unstoppable, winning 24 straight Big Ten matchups to start his career. 

But history has now been altered in the form of a 42-27 win for the Wolverines -- a defining moment for the program and coach Jim Harbaugh. 

Day, on the other hand, is now dealing with his first major obstacle as coach of the Buckeyes. 

Losing on the road against a top-five team in the nation is one thing. Getting physically crushed by your arch rival in the most disappointing loss since a 31-0 drubbing in the 2016 College Football Playoff semifinal to Clemson is quite another. Above all, it hands Ohio State its first real adversity of the Day era. 

Legendary Buckeyes coach Earle Bruce said it best: "If you don't win the Michigan-Ohio State game, buddy, that's a problem. You're not going to be recognized for too much success. We've had 11-1 and 10-1 football teams that lost to Michigan and they're not even mentioned in the second breath." 

Heading into The Big House on Saturday, this seemed like one of those Ohio State teams that could rank among the best in modern history. CBS Sports draft analysts project four different players from the Buckeyes offense alone could be selected in the first round of the 2022 NFL Draft, not even including underclassmen like quarterback C.J. Stroud, running back TreVeyon Henderson or receiver Jaxon Smith-Njigba. 

Losing The Game changes everything about how this team will be viewed historically. 

And it wasn't only a loss. Ohio State gave up 297 yards rushing and six touchdowns to a Michigan offense that threw the ball just 20 times. Three of the Wolverines' six scoring drives went nine plays or more, while all six traveled at least 60 yards. Broken plays and turnovers leading to a fluky loss would have been more palatable, but Day officially has major cracks in the foundation to fix on the defensive side of the ball.

Outside of what now seems like an outlier defensive performance against No. 12 Michigan State, the Buckeyes have struggled to defend teams with a pulse on offense. Minnesota running back Mo Ibrahim rushed for 163 yards and two touchdowns in a season-opening game that only flipped the momentum to Ohio State when he suffered a season-ending injury. Oregon's C.J. Verdell rushed for 161 yards and two touchdowns in an upset victory over the Buckeyes the following week. Purdue quarterback Aidan O'Connell threw for 390 yards and four touchdowns as part of a 31-point effort this month, while Michigan running back Hassan Haskins rushed for 169 yards and five touchdowns on Saturday. 

Ohio State tried shaking things up at defensive coordinator by passing play-calling responsibilities from Kerry Coombs to secondary coach Matt Barnes. That seemed to pay dividends as the Buckeyes held Akron, Rutgers, Maryland and Indiana to a combined 44 points. Unfortunately, the issues are far from fixed. 

If Michigan was an explosive team filled with killer recruits and a dynamic quarterback, that would be one thing. Prior to 2021, Day's only two losses came to national champion Alabama and national runner-up Clemson. Conversely, the Wolverines rank No. 15 in the 247Sports Talent Composite -- Ohio State is No. 3 -- and have just one top-10 class since 2018. You can't out-recruit being punched in the mouth over and over. 

Since Michigan's last win in 2011, Ohio State has dominated the rivalry and kept the Wolverines living in its shadow. Over that period, Michigan has failed to earn a trip to the Big Ten Championship Game or win more than 10 games in a season. The Wolverines have not won a major bowl game and only have one top-10 finish. Ohio State, meanwhile, has done all of those things and more. 

But the crushing loss gives Michigan something more terrifying than a win: an opening. 

When Urban Meyer suffered his shutout loss to Clemson in the College Football Playoff five years ago, he responded by hiring a little-known assistant named Ryan Day to run his offense. Similarly, Oklahoma and Alabama hired Lincoln Riley and Lane Kiffin, respectively, to turn around their offenses after devastating postseason losses. 

After losing to The Team up North and failing to win the Big Ten title for the first time, Day faces his first real test as head coach: figuring out how to adjust the defense. Whether he can return the defense to championship level will define whether the Buckeyes can elevate towards their first championship since 2014 -- or whether they're doomed to stay at a lower ceiling.