Caleb TerBush passed for 178 yards and two touchdowns to help Purdue upset the No. 23 Fighting Illini 21-14 on Saturday.

Two weeks ago, Illinois looked like a solid contender that might hang with Wisconsin and Penn State in the Big Ten's Leaders Division. Then, the Illini (6-2, 2-2 Big Ten) stumbled through a mistake-filled 17-7 home loss to Ohio State and now have lost to Purdue after rolling to a perfect start and being ranked as high as No. 16.

The Illini still can have a very good season -- just not the great one that appeared to be in the works two weeks ago.

"No one on this team is a quitter," coach Ron Zook said. "No players, no coaches, no one on this team will quit."

The Illini scored on a 16-yard run by Jason Ford with 8:12 remaining, and a 2-yard run by quarterback Nathan Scheelhaase cut Purdue's lead to 21-14 with 54 seconds to play.

But Purdue's Justin Siller recovered the onside kick and the Boilermakers ran out the clock.

Illinois' once powerful offense has been stuck in neutral the past two weeks. The Illini were held to 285 yards against Ohio State and 366 yards against Purdue, most of which were gained after they fell behind 21-0.

"We just came out slow," receiver Hayden Daniels said. "We need to come out and play better. If we start out slow, that affects the whole game. We need to be playing hard from the get-go."

Illinois' A.J. Jenkins, who led the nation in yards receiving, finished with eight catches for 92 yards. He never broke anything big, though, as Purdue cornerback Ricardo Allen got the best of their matchup.

Purdue has been playing with confidence. The Boilermakers hit a low with a 38-10 loss to Notre Dame, but rallied with a 45-17 win over Minnesota the next week, a spirited effort in a 23-18 loss at Penn State and now the win over Illinois.

"I thought it was a great team victory," Purdue coach Danny Hope said. "Everyone showed up, everyone played hard. For three weeks in a row now we've taken the field with a lot of energy and a lot of enthusiasm."

Purdue's offensive line protected TerBush from Illinois defensive end Whitney Mercilus, who led the nation with 10 sacks and was tied for the national lead with five forced fumbles. Mercilus was held without a sack.

Illinois' defense, ranked 12th nationally in yards allowed per game coming in, gave up 304 yards, including 229 in the first half.

Purdue squandered an early opportunity when Antavian Edison fumbled after the Boilermakers moved into Illinois territory.

But the Boilermakers got it going again on their next possession. TerBush rolled right to avoid the rush and found Siller downfield for a 32-yard gain. TerBush and Siller later connected again for a 6-yard touchdown that gave Purdue a 7-0 lead with 3:25 left in the first quarter.

Raheem Mostert scored early in the second quarter on a 21-yard run to give Purdue a 14-0 lead with 11:41 left.

Illinois went three-and-out on its next possession, and Mostert tackled Illini punter Justin DuVernois at the Illinois 14. TerBush found Jared Crank in the end zone for a 4-yard touchdown pass to put the Boilermakers up 21-0 with 7:48 left in the half.

Illinois tried to get Jenkins involved, and backup quarterback Reilly O'Toole fired deep to him late in the first half, but Allen intercepted inside the Purdue 10-yard line.

The offense remained stagnant until the fourth quarter, when it was up against Purdue and the clock.

Last year, Scheelhaase passed for four touchdowns and ran for a game-high 118 yards to lead the Illini to a 44-10 win over Purdue. This year, he passed for 217 yards, but ran for just 16 on 13 carries. He was sacked four times and was under constant pressure. Kawann Short led Purdue with two sacks.

"As far as the sacks go, that's probably me holding onto the ball a little too long," Scheelhaase said. "Sometimes, you have to get rid of it or know where your hot route is when they bring blitzes."

Zook said Scheelhaase is only part of the problem.

"I tell him it's not all on him, it's not all his fault," Zook said. "He missed some throws, but all quarterbacks do that. It may be that he is pressing and pushing too hard, but I like this team. This is a good team."

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Follow Cliff Brunt on Twitter: http://www.twitter.com/cliffbruntap