EVANSTON, Ill. — Ohio State’s run game struggled at the start Friday night. So, surprisingly, did its run defense.

It’s a testament to the Buckeyes’ dominance this season that such blips stand out. And blips are all they proved to be.

Ohio State quickly overwhelmed Northwestern 52-3 in front of a Ryan Field crowd containing more scarlet than purple.

The No. 4 Buckeyes improved to 7-0 (4-0 Big Ten) heading into next Saturday’s showdown against unbeaten Wisconsin.

Ohio State quarterback Justin Fields threw for 194 yards and four touchdowns on 18-of-23 passing. J.K. Dobbins finished with 121 rushing yards and scored twice, as did wide receiver Chris Olave.

It was Ohio State’s 32nd victory over Northwestern in 33 games since 1971. But the previous three games between the teams were competitive, including a 45-24 Big Ten championship game last year in which the Wildcats trailed by only three in the third quarter.

Northwestern (1-5, 0-4) entered with a solid defense that had been unable to overcome the Wildcats’ feeble offense. But the Wildcats dominated the line of scrimmage early on both sides of the ball. Dobbins’ first nine carries gained only 22 yards.

The Buckeyes overcame that on the game’s first drive to take a 7-0 lead on a 20-yard pass from Fields to Olave.

The way Northwestern’s offense has played this season, Buckeyes fans might be excused for thinking the game was over. The Wildcats rank 128th out of 130 FBS teams in scoring (14.4 per game).

But they didn’t look terrible at the start. The first five runs by Northwestern running backs gained 54 yards, with the shortest an 8-yarder.

“The first play we had 10 on the field, so that wasn't a good start,” Ohio State coach Ryan Day said. “But they had two weeks to prepare for us. They do a good job. They're very well-coached and they’ve got good players. I thought their backs ran hard at times.”

The surprising running success enabled the Wildcats to get close enough for a 33-yard field goal on their second possession to make it 7-3.

After that, the Buckeyes’ defense yielded little. Northwestern’s longest play from scrimmage went for only 16 yards. Its longest pass completion was a 13-yarder as the Buckeyes outgained the Wildcats 480-199.

Ohio State rode Fields’ arm on a 75-yard drive to make it 14-3. Fields kept the possession alive early when he escaped a sack and threw an off-balance strike to K.J. Hill for a 20-yard completion on third-and-15. He completed four straight passes to end the drive, the final one a 19-yarder to Dobbins, who ran a nice cutback route.

The running game finally got untracked in the second quarter. Taking advantage of blocks by center Josh Myers and left tackle Thayer Munford, Dobbins broke a 68-yard run to the Northwestern 5. Munford was a game-time decision because of injury and didn’t start. But he entered the game on that series, though he was clearly hobbled.

“Thayer is an amazing lineman,” Dobbins said. “He's one of my best buds on the team. All those linemen block so well and they’re tough, too. Thayer's been banged up and still tries to come out there and help the team, and that's what I appreciate about him.”

Dobbins scored on a 5-yard run on the next play to make it 21-3, and the rout was on.

The Buckeyes added another touchdown following a botched snap on a Northwestern punt at the Wildcats’ 15-yard line. Fields again found Olave, this time for an 8-yard touchdown in the corner of the end zone.

The Buckeyes’ biggest celebration of the first half came on their final play. Blake Haubeil kicked a 55-yard field goal, which matched the longest one by a Buckeye in 15 years. Only Tom Skladany in 1975 at Illinois with a 59-yarder has kicked one longer.

After the kick went through the uprights to give Ohio State a 31-3 halftime lead, Haubeil’s teammates mobbed him as they ran back to the locker room.

The Buckeyes padded their lead with a 65-yard drive on the first possession of the third quarter. Austin Mack, who caught three previous passes on the drive, hauled in a 23-yarder for the score.

Ohio State added two fourth-quarter touchdowns. Sevyn Banks set up Chris Chugunov’s 7-yard scoring throw to tight end Jeremy Ruckert with an interception at the Northwestern 11. Master Teague III scored on a 73-yard run.

By that time, most of the Northwestern fans had left, leaving the stadium looking like the second half of an Ohio State spring game.

“That's a good way to start the second half of the season,” Day said. “But I just want to give a shout-out to Buckeye Nation. It was awesome to see these guys out here at the game. You felt them the whole game, and there's nothing like going into a place and feeling your crowd like that.”

brabinowitz@dispatch.com

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