COLUMBUS, Ohio, Nov. 10 - The meltdown happened a few weeks earlier this season for No. 1 Ohio State.

Last season, the undefeated Buckeyes were blown away by Florida in the national title game. This season, the flop came sooner, and perhaps more spectacularly, for the again undefeated Buckeyes.

Behind a relentless defense and four touchdown passes by quarterback Isaiah Williams, unranked and enigmatic Illinois stunned the Buckeyes, 28-21, before 105,453 fans on Saturday at Ohio Stadium.

The loudest roars from this upset may have come from Eugene, Ore., as Oregon will likely leap to No. 2 in the Bowl Championship Series standings. That will mean that the Ducks, who were idle this weekend, would play Louisiana State, the likely new No. 1, in the national title game if the season were to end this weekend.

Wisconsin's victory takes the Big Ten out of the title race, much to the relief of college football fans in the West and South, who have been skeptical of the caliber of the league all season.

Ohio State's loss, combined with Michigan's loss at Wisconsin on Saturday, takes a lot of the luster from the matchup between the Buckeyes and the Wolverines in Ann Arbor, Mich., next weekend. The winner will be the Big 10 champion and will likely head to the Rose Bowl, but the game will have significantly less meaning than it did last season, when both teams entered the game undefeated.

For Illinois (8-3, 5-2 Big 10), Saturday's game was a signature victory for the Ron Zook era, which began with only four victories in his first two seasons before this year. The 28 points were the most scored on Ohio State (10-1, 6-1) since its 41-14 loss to the Gators in the national title game last year.

The victory will resonate for a while, especially after the Illinois players began bouncing up and down on the "O" in the middle of the field at Ohio Stadium. The teams had to be separated.

The Illini got a rare steady performance from Williams, who had been sharing quarterback duties with Eddie McGee after being hurt or ineffective for much of the season.

After giving up touchdowns on the first two possessions, the Illinois defense took over.

Led by the dynamic linebacker J Leman, the Illini flustered Ohio State quarterback Todd Boeckman all afternoon.

In his first year as a starter, Boeckman buckled under the pressure of a taut game. He threw three interceptions, one in the end zone late in the third quarter and another on a fluttering lob pass in the fourth.

The most critical play of the game came with just under seven minutes left. On a fourth-and-1 from its 33-yard line, Illinois lined up to punt. Ohio State called a timeout. But when the Illini returned to the line of scrimmage, Zook had them in an offensiveformation. On the snap, Williams lunged forward for the first down.

From there, Williams iced the game with three more first downs on third-down plays. He extended the drive with a 12-yard run up the middle on a third-and-8. On a third-and-10, he converted yet another first down when he again rushed for 12 yards. He then essentially sealed the game with a 3-yard run on third-and-2.

This marked the second consecutive week that Boeckman had to try to engineer a second-half comeback. He did so successfully against Wisconsin last week behind a strong rushing game.

But when the pressure came this week, Boeckman was not nearly as poised. He had been harassed all day by a stout Illini defense, led by Lehman, who had 12 tackles by the end of the third quarter.

Illinois had taken a 21-14 halftime lead after a late drive, which Williams capped with an 8-yard touchdown pass to Brian Gamble. Williams's third touchdown pass, to Brian Gamble with 17 seconds left in the half, came on a drive in which Rashard Mendenhall converted a fourth-and-1 with a 25-yard run.

The game had opened with a flourish, with touchdowns on the first four possessions. It took Ohio State just 23 seconds and two plays to mow through the Illinois defense. Chris Wells capped the drive with an 11-yard run, but the big play was a 65-yard pass to a wide-open Brian Hartline.

Illinois answered with a touchdown of its own 49 seconds later, with an 80-yard run by Daniel Dufrene setting up a 3-yard touchdown pass to Michael Hoomanawanui.

After each team scored again - Ohio State on a 19-yard run by Maurice Wells and Illinois on a 33-yard pass from Williams to Jacob Willis - the pace slowed. But so did Ohio State's drive toward the national title.