BOULDER, Colo. — Tyler Hansen gave the Colorado Buffaloes more zing, zip and zeal at quarterback.

"The plays break down, Tyler's able to scramble and make something out of nothing," tailback Rodney Stewart said. "I think we need that kind of football."

Out to prove he should have been Colorado's starting quarterback all along, Hansen sure showed he deserves to be the Buffaloes' main man from here on out.

The sophomore signal-caller, who replaced Cody Hawkins — the coach's son — in the starting lineup, ran for a touchdown and threw a TD pass to lead Colorado to a 34-30 upset of No. 17 Kansas on Saturday night.

"The quarterback for CU, he was the difference maker today," Kansas coach Mark Mangino said. "It's unfortunate that they picked this (last) week to take his redshirt off. I think they found their quarterback, that's for sure."

Providing a spark both through the air and on the ground, Hansen threw for 175 yards and ran for 34 yards as Colorado (2-4, 1-1 Big 12) handed Todd Reesing and the Jayhawks (5-1, 1-1) their first loss.

"He did a nice job," Buffs coach Dan Hawkins said. "He made a lot of plays with his legs and made some good throws. Again, what a great kid he is. He and Cody from the get-go were being unselfish and that's one of the cornerstones of our team."

Cody Hawkins was always the first to greet Hansen on the sideline either with high-fives or pats on the back.

"Having two guys like that bodes well for the foundation of this team," Dan Hawkins said.

Reesing was 30-of-51 for 401 yards and two scores, but he was dumped for six sacks and threw an interception that was returned to the 1 and led to Hansen's touchdown on a keeper around right tackle.

It was against Colorado that Reesing made his debut as a freshman in 2006, starting the second half and leading the Jayhawks to a 20-15 win in Lawrence after standing on the sideline for the first eight games.

This time, Hansen led the Buffs to the winning score after Reesing had rallied the Jayhawks from a three-touchdown deficit to give Kansas a 30-27 lead early in the fourth quarter.

Hansen drove the Buffaloes 76 yards in 10 plays, the payoff coming when Stewart scored from 12 yards out, dragging a defender the final five yards into the end zone with 8½ minutes remaining.

Reesing, whose pass to Dezmon Briscoe was broken up by Jimmy Smith on fourth-and-goal from the 6 with 4½ minutes left, got the ball back with 59 seconds remaining and nearly pulled off yet another comeback.

He drove the Jayhawks all the way to the Buffaloes 19 thanks to a 26-yard strike to Briscoe, but after spiking the ball with seven seconds left, his final two passes were knocked away by the Buffaloes.

Cornerback Jalil Brown tipped away a pass intended for Kerry Meier, who caught 11 passes for 103 yards, with three seconds left. Then, Reesing went to Briscoe again, and this time, cornerback Cha'pelle Brown batted it down as time expired and the crowd stormed the field, celebrating Colorado's biggest win in a year.

For once, the Buffs had an answer to Reesing in their own scrambling quarterback.

"That's a huge advantage for the offense to have a guy back there that, when things start to break down, receivers can get open," Colorado linebacker Jeff Smart said. "Because it's challenging to cover guys for three, five, 10 seconds, especially when they start making up routes."

Hansen lost out to Hawkins in August but his redshirt was stripped last week when he came off the bench to play at Texas.

After a slow start for Kansas, Reesing executed to 2-minute offense to perfection at the end of the second quarter, driving the Jayhawks 80 yards in eight plays, capped by a 4-yard strike to Meier to pull Kansas to 27-10 at the half.

That was the first of five consecutive drives that ended in points for the Jayhawks, who managed only a field goal in their first seven possessions, capped when Reesing hit Briscoe with a 25-yard scoring strike to give the Jayhawks a 30-27 advantage.