BOULDER, Colo. -- Ninth-ranked Colorado won the Pac-12 South title Saturday with a 27-22 win over No. 21 Utah thanks to a senior-laden defence that forced two huge fumbles by Utes star running back Joe Williams. Cornerback Chidobe Awuzie also had a touchdown-saving tackle after a 93-yard kickoff return.

"I'm very excited to grind one out," said Colorado quarterback Sefo Liufau, who fumbled twice. "The defence got my back."

The Buffaloes (11-2, 8-1, No. 9 CFP) will face sixth-ranked Washington in the conference championship next weekend.

With the first sellout crowd in Boulder since 2008 itching to storm the field, the Utes (8-4, 5-4) pulled to 27-22 on Demari Simpkins' 7-yard TD catch with 1:34 remaining. That capped an 80-yard drive that included two fourth-down conversions and was done largely without Williams, who hobbled off for the second time with an apparent shoulder injury.

The 2-point conversion toss by Troy Williams was incomplete, and the Utes' onside kick failed when Kabion Ento recovered for Colorado, which ran out the clock to complete its worst-to-first revival in one of college football's biggest comeback stories in recent years.

"Nobody thought we'd be here, especially four years ago," said CU senior safety Tedric Thompson, who had two interceptions and broke up four passes.

As soon as the clock hit all zeros, thousands among the crowd of 52,301 ignored the public address announcer's plea to wait a minute before storming the field.

Linebacker Kenneth Olugbode scooped up Joe Williams' second fumble and returned it 10 yards for a TD that made it 27-16 early in the fourth quarter.

In the third quarter, Awuzie recovered when Williams fumbled at the Colorado 2 after a 12-yard gain.

"Joe was a huge part of our success this season," Utah coach Kyle Whittingham said. "He was a huge value to our football team. He struggled tonight, put the ball on the ground a few times. But I love Joe Williams."

Liufau's 6-yard TD toss to Shay Fields on the final play of the third quarter was the senior's 60th, tying Cody Hawkins' school record and breaking a 13-13 tie.

Kyle Fulks returned the ensuing kickoff 93 yards but a diving Awuzie knocked Fulks out of bounds at the 3, a tackle that proved pivotal when the Utes had to settle for a field goal that made it 20-16.

THE TAKEAWAY

Utah: The Utes had another fine season but they lost three of their last four games with close defeats at home to Washington and Oregon before losing in Boulder for the first time since Sept. 28, 1957.

Colorado: The Buffs held Joe Williams to 97 yards on 26 carries, 58 yards below his average, and they limited Troy Williams to 160 yards on 13 of 40 passing. So, they roll into the Pac-12 title game on the strength of their first six-game winning streak since 1996, their first 10-2 record since 2001 and their first undefeated record at home since 1994.

POLL IMPLICATIONS

The Buffs could inch up in the poll and the Utes did nothing to merit slipping.

LUCKY FLIP: The Buffaloes improved to 11-1 -- on the coin toss. They deferred to the second half. The only time Colorado lost the coin flip this year was against USC.

UP NEXT

Utah: Despite a second straight loss, the Utes await another bowl bid, their 11th in 14 seasons under Whittingham.

Colorado: The Buffaloes will face Washington in the Pac-12 championship game next Friday in Santa Clara, California.