Ohio State reached the halfway point of the regular season Saturday night and finally got a real test.

That it came against Michigan State wasn’t a huge surprise, given the Spartans’ history against the Buckeyes. But this would not be 2013 or 2015, when Michigan State crushed Ohio State’s championship hopes.

The No. 4 Buckeyes shook off a slow start on offense with a 24-point second-quarter explosion and defeated the No. 25 Spartans 34-10 in front of 104,797 at Ohio Stadium.

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

Ohio State improved to 6-0 (3-0 Big Ten) as it enters an off week before playing at Northwestern.

“I feel like we beat a top-25 team in a great atmosphere — a really well-coached team, a really good defense, a really good quarterback,” Ohio State coach Ryan Day said. “To hold them to 285 (yards) and to have 529, that’s a good day. I think the best part about that is we all kind of got off the field feeling like we can’t wait to get (back) on the field to figure out where we can improve.”

Justin Fields completed 17 of 25 passes for 206 yards, including touchdown passes of 60 yards to Binjimen Victor and 21 to tight end Luke Farrell.

J.K. Dobbins ran for 172 yards on 24 carries, including a 67-yarder for a score.

All of those came in the second quarter after an opening 15 minutes in which the Buckeyes bore little resemblance to the offensive machine they’d been in their first five games.

>> Post-game video: Ryan Day discusses win over Michigan State

Michigan State (4-2, 2-1) entered the game with the seventh-ranked defense nationally and played like it early. The Spartans won the battle at the line of scrimmage and pressured Fields. The Buckeyes didn’t get a first down until their fourth possession and gained only 16 yards in 16 first-quarter snaps.

“It was not a good quarter of football on offense,” Day said. “When you’re playing a team like Michigan State, things like that are going to happen. You have to respond, and I thought we did.”

Thanks to Michigan State turnovers, Ohio State was able to take a 3-0 lead anyway. After Blake Haubeil missed a 37-yard field goal try following the first turnover, he made a 39-yarder after the second — a Davon Hamilton fumble recovery at the Michigan State 22-yard line.

The offense finally came alive early in the second quarter. The Buckeyes moved from their 14 to the 40. Fields then rolled out as if to run, and Michigan State's David Dowell and Antjuan Simmons bit on the fake. Fields helped sell it by tucking the ball as he left the pocket.

That left Victor open. Fields lobbed him the ball and he broke a tackle and dived into the end zone for a 60-yard score.

But just as Ohio State’s fans began to exhale, Michigan State drove 75 yards in only five plays, capped by a 20-yard pass from Brian Lewerke to Darrell Stewart.

Ohio State answered with a 75-yard touchdown drive of its own. Fields scrambled for 35 yards on third down to start the possession. He finished it by throwing to Farrell, who caught the ball at the 10 and fought off Michigan State tacklers for a 21-yard touchdown. It was only his second catch of the season.

After Michigan State kicked a field goal to make it 17-10, J.K. Dobbins broke a 67-yard touchdown run.

The play looked designed for Dobbins to cut left behind the blocks of left guard Jonah Jackson and center Josh Myers. But Dobbins cut right to find daylight. Cornerback Josiah Scott looked like he'd make a touchdown-saving tackle, but when he tried to punch the ball out, Dobbins broke free to the end zone.

“That was a home-run hit right there,” Day said. “That really changed the game.”

The Buckeyes added a 43-yard field goal at the end of the second quarter for a 27-10 halftime lead. Ohio State gained 296 yards in the second quarter.

“We just started out rough,” Fields said. “The offense, we were kind of killing ourselves. We got back together in the second quarter and did what we were supposed to do. We didn’t make any adjustments. We just did what we were supposed to do and executed.”

Michigan State drove to the Ohio State 9 on its first possession of the third quarter, but Matt Coghlin’s 27-yard field goal attempt was wide left.

Ohio State had a chance to pad its lead on its ensuing drive when it moved inside the Spartans’ 30, but Fields threw his first interception as a Buckeye on an overthrown pass to K.J. Hill, who didn’t appear to see the ball coming.

But Ohio State’s defense didn’t let Michigan State threaten the lead. It forced a three-and-out and then stopped the Spartans at midfield on their next possession.

The Buckeyes then went 80 yards in 11 plays to end any suspense about the outcome. Fields scored on a 1-yard keeper, keeping alive his streak of passing and running for a touchdown in all of his starts.

“To beat a team like this, you have to play tough,” Day said. “We talked about it going into the game, and I thought we did.”

brabinowitz@dispatch.com

@brdispatch