Days after reclaiming the top spot with a win over Michigan, top-ranked Indiana (20-3, 8-2 Big Ten) fell to Illinois 74-72 at the buzzer, with students spilling on to the court to celebrate as an official review confirmed the layup by Tyler Griffey.
"Is anybody else as tired as I am?" Illinois coach John Groce asked the media, somewhat joking, following the game.
It was just another surprising night in college basketball, with the No. 1 team in the country losing for the fifth week in a row.
"They're very deserving of the win because they never gave in," Hoosiers coach Tom Crean said.
"We didn't put them away when we had our opportunities. That's the bottom line."
The Illini inbounded the ball with 0.9 seconds left in the game, with Griffey flashing to the basket wide open after what Indiana coach Tom Crean called a "miscommunication" on defense.
Fellow senior Brandon Paul hit Griffey with the pass and the senior forward beat the buzzer with a simple right-handed lay-up.
"It was one of our standard (plays)," Griffey detailed to the press, as Paul tried to cut him off from revealing any secrets.
The truth is, there was no secret twist. The play is an often-used set and was run because Illinois (16-8, 3-7 Big Ten) was out of timeouts and couldn't draw up anything special.
"I just made a simple curl cut and left two guys behind me, and I just got it off before the buzzer."
Following the game, Crean defended his strategy of not calling a timeout.
"I wouldn't change that for a second," he said. "We just didn't communicate with the switch there at the end."
The students immediately rushed the floor, kicking off a wild celebration that paused briefly for officials to confirm the basket. The scene included Groce being knocked to the ground at one point, as Griffey was hoisted on the shoulders of both teammates and fans.
Paul and senior D.J. Richardson, who scored a game-high 23 points, shared an emotional embrace, as tears began to replace smiles before taking to the scorers table to make sure those still in the stands could see, too.
"I'm happy for our players," Groce said. "I'm most happy for our seniors."
Having lost six of the last seven, Illinois was a long shot to pull off the upset.
And senior Tyler Griffey had perhaps the longest of odds to command the spotlight at the end.
Stripped of his starting role in the midst of a shooting slump that saw 20 straight misses from the 3-point line in the previous eight games, Griffey hadn't scored in double figures since Dec. 22.
He logged a season low eight minutes and failed to score Sunday in a loss to Wisconsin.
He finished with 14 points and eight rebounds, logging a season-high 31 minutes.
"I just said to myself, finally," Griffey said of his thoughts after hitting his first of two 3s in the second half. "I've gotten a lot of shots up between when I started missing until now, so much so that my wrist has been hurting."
Richardson continued a comeback that looked to have stalled with a little more than three minutes remaining in the game. Trailing by eight, Richardson hit two 3s and a 15-footer on three straight possessions to tie the game at 70.
Indiana's Victor Oladipo answered with a layup, but fouled Paul on the subsequent possession.
At the free-throw line, Paul used some luck to keep the Illini's hope alive.
A 72 percent free-throw shooter, Paul banked in the first shot and swished the second.
That set up Indiana's final possession. Oladipo made his move to the basket with less than 10 seconds remaining, but Richardson cut him off and stole the ball.
Oladipo raced back to block a Richardson layup attempt out of bounds, which set up Griffey's shining moment.
Indiana was left wondering what happened after leading for most of the game and taking a double-digit advantage with less than five minutes to play.
The Hoosiers shot 50 percent for the game, but allowed the Illini to score 28 points off of 14 turnovers.
When asked of the difficulty of playing the No. 1 team in the country, Crean couldn't readily provide an answer.
"That's a hard question," he said. "I'm not sure. I just know these games are 40-minute games.
"I'm proud of our guys. I'm never going to roll anybody under the bus. We're going to get better from this."