Gilreath took the game's opening kickoff 97 yards for a touchdown and Wisconsin tallied a pair of rushing touchdowns from junior tailback John Clay to take a 21-0 lead at the 10:04 mark of the second quarter.
Clay's second touchdown capped a 19-play, 89-yard drive against an Ohio State defense that was battered and bullied by the Badgers' offensive line. The Buckeyes entered the game as the nation's fourth-toughest defense to run on, allowing an average of only 78.7 yards over their first six games. Wisconsin eclipsed that total by the 3:15 mark of the first quarter and finished with 184 yards on the ground.
Ohio State managed to make a game of it in the second half, roaring back to pull with three points thanks to a pair of touchdown runs from junior tailback Dan "Boom" Herron. But after the Buckeyes closed to within 21-18 with 11:38 remaining in the game, the Wisconsin offense shifted gears and closed things out with a couple of ball-control possessions that left OSU with no time left for a comeback.
"Wisconsin did the things they needed to do to win the game," OSU head coach Jim Tressel told reporters after the game. "It started with special teams and they ran the ball well. I'm proud of our kids who fought hard and fought back when maybe a lesser bunch would have folded their tent. We got it back to 21-18, but to Wisconsin's credit they … came up with the win."
The Badgers hadn't had much success over the years against top-ranked teams, entering the game with a 3-16 record all-time against No. 1-ranked opponents, but all of their victories over top-ranked teams have come at Camp Randall Stadium. The last time Wisconsin had beaten a No. 1 team came in the 1981 season opener when the Badgers handed Michigan a 21-14 upset loss in Madison.
For Ohio State, it was the first time its defense had allowed a Big Ten opponent to crack the 30-point mark since a 42-39 win over Michigan in the 2006 regular-season finale. Additionally, they allowed a 100-yard rusher for the first time in 29 games when Clay finished with 104 yards on 21 carries.
The loss wasted excellent performances by Herron and senior receiver Dane Sanzenbacher. Herron rushed 19 times for 91 yards and the two scores while Sanzenbacher had six catches – many of them crucial, acrobatic grabs – for 94 yards.
OSU junior quarterback Terrelle Pryor had an excellent third quarter when he completed all seven of his pass attempts for 86 yards as the Buckeyes were in rally mode. But Pryor seemed out of sync most of the rest of the evening and finished 14 for 28 passing for 156 yards, no touchdowns and one interception. He added 56 rushing yards on 16 carries.
His Wisconsin counterpart, Scott Tolzien, was an efficient 13 for 16 for 152 yards, no touchdowns and an interception.
The Badgers wound up with 336 total yards while the Buckeyes had 311.
Gilreath electrified the home crowd on the game's opening kickoff, taking it at his own 3 and exploding up the middle. The 5-11, 169-pound senior made on defender miss and raced virtually untouched to the end zone. Wisconsin kicker Philip Welch came on to add the extra point and the Badgers were off and running with a 7-0 lead a mere 22 seconds into the ballgame.
Ohio State started out well with its first possession when Pryor connected with junior wideout DeVier Posey on a 14-yard pass. But on the next play, Pryor pitched high and behind Herron on an option, and although OSU was able to corral the loose football the play went for a 12-yard loss.
That was indicative of the sputtering OSU offense in the early going as the Buckeyes accounted for only 35 yards in the opening period.
Meanwhile, the Badgers' running game was gashing the Ohio State defense. Clay capped a six-play, 58-yard drive with a 14-yard touchdown run on which he was barely touched, and Welch's PAT made it 14-0 at the 10:00 mark of the first quarter.
Then after Ohio State's next possession resulted in a punt, Wisconsin embarked on its 89-yard drive that ate up an amazing 10:04 off the clock. When Clay dove over from the 1-yard line and Welch kicked another extra point, the Badgers were sailing along with a 21-0 advantage with 10:04 still left until halftime.
The Buckeyes finally showed some life on offense, getting the ground game geared up after a 17-yard scramble from Pryor on a third-and-9. Herron broke off runs of 14 and 16 yards to give his team a first-and-goal at the Wisconsin 3.
But OSU was stopped on three successive running plays – two by Pryor and one by Herron out of the Wildcat formation – and the Buckeyes wound up settling for a 21-yard field goal from senior kicker Devin Barclay.
That made it 21-3 with 6:48 remaining in the half, and Ohio State got another scoring chance less than two minutes later when junior linebacker Andrew Sweat picked off a Tolzien pass and returned it 18 yards. A subsequent personal foul penalty against the Badgers gave OSU excellent field position at the Wisconsin 23 but the Buckeyes couldn't cash in.
On third-and-9, UW defensive end J.J. Watt blew past OSU right tackle J.B. Shugarts to sack Pryor for a 6-yard loss, and Barclay's 45-yard field goal attempt sailed just outside the left upright.
The third quarter featured a complete turnaround for the Buckeyes as they took the opening kickoff of the second half and marched 77 yards in 10 plays to cut into Wisconsin's lead. Sanzenbacher made a leaping catch for a 24-yard gain during the drive, and Herron capped things by taking another direct snap and motoring 13 yards into the end zone.
When Barclay added the extra point, the Buckeyes had climbed within 11 points at 21-10 at the 10:08 mark of the third quarter.
They got even closer on their longest drive so far this season, a 19-play march that covered 94 yards and took 9:50 off the clock. Herron finished things off with a 1-yard TD run, and then Pryor executed a perfect fake before lofting a pass to sophomore tight end Reid Fragel for the two-point conversion.
That made it 21-18 with 11:38 remaining in the game and momentum clearly on Ohio State's side.
But the Badgers seized it back with a 10-play, 73-yard touchdown drive that broke the back of the OSU defense. UW receiver Nick Toon beat Ohio State cornerback Chimdi Chekwa for a 20-yard gain on a crucial third-and-3 play early in the possession, and Wisconsin put into overdrive after that.
Freshman tailback James White scored on a 12-yard run with 6:57 to go, and once Welch added the extra point, the Buckeyes were down by 10 again at 28-18.
Needing to come up with some late-game heroics, OSU came up empty. The Buckeyes' ensuing possession was a three-and-out, and Wisconsin added a 41-yard field goal from Welch at the 4:14 mark to make it 31-18.
Pryor tried gamely to get one last score, but his attempt to Sanzenbacher inside the 1:30 mark was underthrown and intercepted by Wisconsin linebacker Blake Sorsenson.
Ohio State (6-1, 2-1) will return home next Saturday to play Purdue (4-2, 2-0), which scored a 28-17 win over Minnesota earlier today. Kickoff for the annual OSU homecoming game is set for shortly after noon Eastern.