One week.

That’s how long the Ohio State Buckeyes’ reign atop the college football world lasted.

Their short-lived rule came to a crashing halt Saturday night in a 31-18 loss to No. 18 Wisconsin (6-1, 2-1) in Madison, Wis.

The Buckeyes (6-1, 2-1) couldn’t have scripted a worse start, as they fell behind 21-0 early in the second quarter.

OSU overcame a fourth-quarter deficit at Camp Randall Stadium in 2008, when quarterback Terrelle Pryor captained an 80-yard drive in the closing minutes to escape Madison with a 20-17 victory.

There would be no heroics this time around.

OSU scratched to within 21-18, but a 12-yard touchdown run by freshman James White midway through the fourth quarter put the game out of reach, giving Wisconsin its first win over a No. 1 team since a 1981 victory against Michigan.

“We’ve been in four-quarter games this season, and I didn’t really think Ohio State had been,” Wisconsin coach Bret Bielema said.

The Badgers wasted no time in jumping out to an early lead. Receiver David Gilreath returned the opening kickoff 97 yards for a touchdown.

“Nothing against our special teams, but that really hurt us,” Pryor said. “That kicked us in the rear end.”

With the return, Gilreath became the Big Ten’s all-time leader in kickoff return yardage.

“He has been one of those guys all along who’s been one tackle away or one break away,” Bielema said. “That play that we ran on opening kickoff, it was something that he felt good about all week.”

Special teams blunders aside, it was the Buckeye defense that hindered OSU’s efforts.

Wisconsin’s John Clay rushed for 104 yards and a pair of touchdowns. White gained 75 yards on 17 carries.

It’s the first time the Buckeyes have allowed a 100-yard rusher since USC’s Joe McKnight torched OSU for 105 yards on Sept. 13, 2008, a span of 29 games.

OSU limited Clay to just 59 yards on 20 carries in last year’s meeting, a 31-13 Buckeye victory at Ohio Stadium.

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Clay scored his touchdowns on consecutive drives in the first half, the second coming on a 19-play, 89-yard march that pushed Wisconsin’s lead to 21-0.

“They took advantage of our weaknesses and capitalized,” OSU defensive lineman Cameron Heyward said. “They made some great plays when they needed to and they were able to move the ball.”

The Buckeye offense never found a rhythm, either.

One week after throwing for a career-high 334 yards, Pryor managed just 156 yards through the air, completing only 14 of his 28 pass attempts.

He struggled to connect with his receivers, often leaving throws short or forcing passes into tight coverage. Senior Dane Sanzenbacher hauled in six catches for 94 yards, but paid the price on several occasions, taking several big hits.

Only when Dan Herron began to find running lanes in the third quarter did the Buckeyes consistently move the ball. Herron finished with 92 yards and two touchdowns, his sixth straight game with a score.

But by then, OSU had dug itself into too deep a hole.

Trailing 31-18 and driving with slightly more than a minute remaining, Pryor threw an interception, the Buckeyes’ only turnover.

Pryor’s counterpart, Wisconsin senior Scott Tolzien, wasn’t spectacular, but was efficient. The senior completed 13 of 16 passes for 152 yards. Junior receiver Nick Toon had six catches for 72 yards.

Tolzien’s lone miscue – a second-quarter interception by OSU linebacker Andrew Sweat – went for naught after kicker Devin Barclay missed wide left on a 45-yard field goal attempt.

A sea of Badger fans stormed the field following the final kneel-down.

“To beat the No. 1 team and beat a ranked opponent, it’s good,” Bielema said. “There were a lot of potential recruits here, and being on national TV, I’m sure we got some good exposure.”

OSU returns home Oct. 23 to host Purdue, the last opponent to knock off the Buckeyes before Saturday.

“We just have to stop taking stuff for granted,” Pryor said. “We have to get back in the film room and figure out what we did wrong and get ready for Purdue.”