Manhattan ? Brock Jensen backed into the end zone for the go-ahead touchdown with 28 seconds left, and North Dakota State upset defending Big 12 football champion Kansas State, 24-21, Friday night.

The senior quarterback led the Bison on an 18-play, 80-yard march that ate 81/2 minutes, helping them convert four third downs along the way, and left the Wildcats with virtually no time left to set up a tying field-goal try.

Jensen threw for 165 yards and two touchdowns for the Bison, the two-time defending FCS national champions who have beaten Colorado State, Minnesota and Kansas in the last three years.

Jake Waters threw for 280 yards and two touchdowns for the Wildcats, who built a 21-7 lead by the third quarter before everything fell apart. Waters was picked off twice, including a desperation heave after the Bison had taken the lead to wrap up the biggest win in North Dakota State history.

When the final gun sounded, the Bison raced to midfield to celebrate, and then headed to the corner of the end zone that was painted yellow by their fans — a strong contingent in the crowd of 53,351, the second-largest ever to see a game at Kansas State.

Sam Ojuri had 10 carries for 127 yards, and John Crockett also ran for 50 yards for the Bison. Ryan Smith caught eight passes for 72 yards and a touchdown.

It was a glum way for the Wildcats to wrap up a festive day on campus.

The school dedicated a $90 million renovation to the west side of Bill Snyder Family Stadium in a ceremony attended by Gov. Sam Brownback and Sens. Pat Roberts and Jerry Moran. Along with a ribbon-cutting, the school also unveiled an 8-foot bronze statue of its beloved coach.

Snyder even made the rare decision to leave his team on game day for a few hours to attend the ceremony, but joked that if the Wildcats stumbled “it’s all going to be on my shoulders.”

Then again, perhaps the 73-year-old Snyder wasn’t joking at all.

Kansas State struggled early on with Waters under center, punting on its first two possessions and then failing to pick up a first down on fourth-and-3 from the North Dakota State 26. The offense simply couldn’t find a rhythm the way it seemed to under Heisman Trophy finalist Collin Klein.

The Bison took advantage of the lull — and a 49-yard punt return by Christian Dudzik — to take a 7-0 lead on Jensen’s 5-yard pass to Smith late in the first quarter.

The Wildcats finally got on the board when Waters completed four straight passes, capped by a 45-yard touchdown toss to Thompson early in the second quarter. But both teams squandered chances to seize a halftime lead — Waters was picked off deep in his own territory, only for the Kevin Vaadeland to drop a TD catch and Adam Keller to clang a field-goal attempt off the left upright.

Kansas State threatened to break the game open in the third quarter.

Waters followed a couple short completions with a 56-yard touchdown pass to Lockett, who had run right past Williams to get open. On the ensuing series, backup QB Daniel Sams made his season debut on third-and-3 at the Bison 17 and ran almost untouched for a touchdown that made it 21-7.

North Dakota State was on the ropes when Jensen engineered a 12-play, 75-yard touchdown drive that he capped with a 9-yard pass to Vaadeland. The Bison twice converted short third downs.

Keller atoned for his miss by hitting from 41 yards to make it 21-17 after three quarters.

The Wildcats were still clinging to that lead when North Dakota State got the ball back in the fourth quarter. Jensen methodically led the Bison downfield, picking up a first down at every key juncture, and then used his legs to carry them into the end zone for the go-ahead score.