Dayton jumped out to a 23-9 lead behind excellent shooting and never let up. The Flyers shot 48.1 percent from the field, including 8 of 18 from 3-point range.
"To be honest, after watching film and seeing them play, they should probably be playing in the (NCAA tournament)," Dayton coach Brian Gregory said. "I have an unbelievable amount of respect for (coach) Bruce (Weber) and the way his team played and the type of guys he has in his program. And that just means, to me, makes this victory even more satisfying because we beat a really good team on their home court."
The Illini's struggles to get back on defense led to quick, easy baskets for Dayton. Illinois trailed by as many as 16 points before cutting it to four with 18 seconds left.
"They got the ball out quicker than we expected," said Illinois guard Demetri McCamey, who shot 6 of 19. "We knew it was going to be kind of like Michigan State.
"The wings were flying, getting to the basket. They caused us problems in the first half."
D.J. Richardson's 3 to open the game was Illinois' lone lead of the night. Dayton answered with a 9-0 run that forced the Illini to play catch up the rest of the way, and the Flyers led 38-25 at halftime.
Despite a size advantage, Illinois' big men never got on track. Junior center Mike Tisdale fouled out with 7:53 left and finished with six points on 3-of-6 shooting and three rebounds. Mike Davis, coming off a double-double against Kent State, had seven points and eight rebounds.
Dayton used its deep bench to press man-to-man in the first half, subbing in waves and keeping players fresh. No Flyer played more than 30 minutes, while nine logged at least nine minutes. Six scored eight or more points.
"We played with great intensity and energy today, and I thought that was the difference in the game," Gregory said.
Johnson was 4 for 11 from the field but 9 of 10 at the foul line.
McCamey had 13 points and 10 assists for No. 1 seed Illinois (21-15).
The game was a microcosm of Illinois' season: a slow start with inconsistent shooting and a frantic comeback. And with the season now over, Weber and his squad have plenty of time to reflect on a disappointing year that began with NCAA tournament aspirations.
"If we want to be a team and be successful, we got to work on offense, moving without the ball and especially defense, getting stops in key points of the time," McCamey said. "I think overall we need to work on everything and just become better players and work hard this summer."