Sportsbooks were noticing something unusual heading into the first NFL weekend of the season: a college football game involving two unranked teams was the most popular bet on the board.

Sportsbook operator BetMGM reported Friday that Colorado-Nebraska had attracted more bets than every remaining NFL game in Week 1 -- a rarity, according to bookmakers, especially for a matchup that didn't look overly attractive before the year.

The bulk of the betting action, upwards of 90%, was on the favored Buffaloes. At PointsBet/Fanatics, more money had been bet on Colorado minus the points against the Cornhuskers than had been bet on 30 NFL teams, with only the Kansas City Chiefs and Detroit Lions, who played Thursday, garnering more support from bettors.

The Buffaloes were consensus 2.5-point home favorites over Nebraska on Friday, a line that has moved dramatically since the summer, when sportsbooks had the Cornhuskers listed as 9-point favorites over Colorado. But after upsetting TCU last week as 21-point underdogs, coach Deion Sanders and the Buffaloes are the betting public's darlings.

"Every time I have glanced at the college football ticker since Saturday, I have seen a line of Colorado bets," Joey Feazel, lead college football trader for Caesars Sportsbook, told ESPN. "The action has been crazy."

The buzz surrounding the Buffaloes at sportsbooks began in the offseason, as Sanders revamped the roster. It went to another level after the upset of TCU. Bets on two-way star Travis Hunter and quarterback Shedeur Sanders to win the Heisman Trophy have poured in at sportsbooks this week, causing dramatic line movement. Hunter has moved from 80-1 to 16-1; Sanders has gone from 100-1 to 22-1 at Caesars Sportsbook.

Colorado-Nebraska is by far the biggest betting game on a college football slate that includes Texas at Alabama. At PointsBet/Fanatics, more money had been bet on just Colorado than had been bet on the Texas-Alabama point spread overall. And at DraftKings, approximately twice as much money had been on Colorado-Nebraska as had been wagered on any other college game.

Ethan Useloff, a trader for PointsBet/Fanatics, said entering the season, there had been more bets on Colorado, a 100-1 long shot, to win the national championship than powerhouses such as Ohio State and Georgia.

"They are being backed as if they were one of the favorites to win it all," Useloff told ESPN.