CHAMPAIGN, Ill. -- James McCourt kicked a 39-yard field as time expired and Illinois Fighting Illini pulled off the biggest upset of the college football season, knocking off No. 6 Wisconsin Badgers 24-23 on Saturday.

Tony Adams intercepted Wisconsin quarterback Jack Coan at midfield with 2:33 remaining. Dre Brown's tackle-breaking 13-yard run got Illinois (3-5, 1-3 Big Ten) to the Wisconsin 25 and allowed the Illini to run down the clock to attempt the game-winner.

McCourt's kick was right down the middle to give coach Lovie Smith the most significant victory of his four-year tenure in Champaign.

The Illini closed as 30.5-point underdogs at Caesars Sportsbook. According to ESPN Stats & Info, Illinois became the first team to win outright as more than a 30-point underdog since Iowa State (+30.5) did it against No. 3 Oklahoma on Oct. 7, 2017.

Wisconsin had not trailed this season and was looking to roll into a showdown with No. 3 Ohio State next week in Columbus. Instead, the Badgers (6-1, 4-1) blew a nine-point lead in the final 9:46 of the fourth quarter.

Illinois beat a ranked team for the first time since 2011 and knocked off a ranked Big Ten team for the first time since 2007, when the Illini beat No. 1 Ohio State in November on their way to a Rose Bowl appearance.

The Illini last beat a ranked Big Ten team at home on October 2007 -- a 31-26 victory against No. 5 Wisconsin.

Heisman Trophy contender Jonathan Taylor rushed 28 times for 132 yards and one touchdown for Wisconsin, but he also had a fumble in Illinois territory in the fourth quarter to help fuel the Illinois comeback.

Coan was 24 of 32 passing for 264 yards and a touchdown, but his one interception came at a crucial time. His pass on third-and-5 sailed high, and Adams grabbed it to give Illinois a short field against the No. 1 defense in the nation.

Illinois had cut Wisconsin's lead to 20-14 late in the third quarter on a 43-yard touchdown run by Reggie Corbin.

Wisconsin had opportunities to pad its lead, but settled for a field goal after a first-and-goal from the 3. Taylor also fumbled at the Illinois 25.

After the fumble, the Illini ripped off a 75-yard touchdown drive, capped by Brandon Peters' 29-yard pass to Josh Imatorbhebhe to make it 23-21 with 5:53 left.

UP NEXT

Wisconsin: The Badgers head to Ohio State for a game that lost a lot of luster in Champaign.

Illinois: The Illini travel to Purdue, trying to make it two straight in the Big Ten.

The Associated Press contributed to this report.