Kansas coach Roy Williams and his bench know their season is coming to an end.(AP)

Illinois (27-7) will play Arizona, the No. 2 seed, Sunday in the Midwest Regional final. It'll be their third meeting of the season, with each team having won once. The Wildcats beat Mississippi 66-56 earlier Friday night.

"It was not the prettiest of games to say the least," said Illinois coach Bill Self, who became the first coach to take different teams to the final eight in consecutive years. He guided Tulsa to the Midwest final last year, then took over the Illini in June after Lon Kruger went to the NBA's Atlanta Hawks.

"I felt like our bench did a great job, but our defense set the tone in the first half," Self said. "We never let their guards get in a rhythm. In the second half, we just hung in there and toughed it out."

Kansas (26-7) ended its longest tournament run since '97. After trailing by 14 early in the second half, the fourth-seeded Jayhawks got within five twice, then were outscored 10-0 during the final 1:24 to make the game look more lopsided than it really was.

"We weren't able to get offensive rebounds, which has been a big part of our offense all year," said Kansas coach Roy Williams, whose season began with his decision to stay in Lawrence instead of going to coach his alma mater North Carolina.

"Their physical size and rebounding ability took us out of our game plan. Illinois made us play less than a perfect game, to say the least."

The 16-point loss was the worst tournament defeat for Williams in 37 NCAA games spanning 12 seasons.

Illinois, which last weekend beat Northwestern State by 42 and Charlotte by 18, is enjoying its best run in the tournament since reaching the Final Four in 1989, the only other time the school was seeded first. The Illini and Michigan State give the Big Ten two teams among the final eight.

Williams, the Big Ten player of the year, hit 11-of-24 shots, including 3-of-7 on 3-pointers, and all five free throws he attempted. His previous career high was 27 -- against next-round opponent Arizona.

"It all came down to my teammates giving me the confidence to go out and gamble on offense," Williams said.

The Illini needed his big night to offset Cory Bradford going 1-of-13, including 1-of-9 on 3-pointers. Sergio McLain had 10 points and 10 rebounds and Illinois got 28 points from its vaunted reserves, with Luke Johnson contributing 15 points and eight rebounds.

Nick Collison led Kansas with 23 points, but he hurt the Jayhawks down the stretch by missing five straight free throws. He was 6-of-14 at the line and the Jayhawks were a wretched 18-of-35. They also were outrebounded 45-33 after averaging 27 more boards than their opponents last weekend.

Drew Gooden, who averaged 18.5 points in the first two rounds, had 13 points and nine rebounds. Kirk Hinrich, his game thrown off by chasing Williams, fouled out with 13 points and six rebounds.

"They were pretty tough out there," said guard Jeff Boschee, who had three points on 1-of-7 shooting, all 3-point attempts. "We were pretty tired out there, but you have to be mentally tough. It's as good of a man defense as we've played."

Illinois stole control early with tight defense and quick hands. The Illini forced the Jayhawks, who average 16 turnovers a game, to commit 14 turnovers in the opening half, stealing eight of them.

Illinois used nine turnovers in a 4:33 span to trigger an 11-0 run. Along the way, Kansas went almost 10 minutes between field goals and took just four shots in the first nine minutes.

"We felt like it had to be an ugly game," Self said. "We knew if it got physical, we could win it with our bench. We went on an 11-point run at the beginning of the game and all of our points came off our defense."

The Illini could've blown the game open, but players kept missing open shots. They'd often fake their defender into the air, step aside and clang the ball off the iron or backboard.

With Illinois making only five of its first 20 shots, the Jayhawks sneaked within two at 23-21 about five minutes before halftime. Then Williams hit two 3-pointers and the Illini pulled out to a 41-29 lead at the break.

There were few highlights in a second half that was bogged down by 15 fouls by Illinois and 13 by Kansas.