Princeton's defense gets a big stop on the game's final possession as it upsets No. 17 Arizona State. (0:31)

With five losses on Saturday's schedule, the men's college basketball season went from bad to worse for the Pac-12, which is assured of the worst December by a major conference in the past 20 years.

Coming off a winless NCAA tournament last March, the Pac-12 will be the first of the Power 5 conferences plus the Big East to finish December with a win percentage below .600 in the past two decades.

Fresh off beating No. 1 Kansas last week, Arizona State -- the conference's only ranked team, at No. 17 -- fell at home to Princeton 67-66. Meanwhile, Utah was thrashed at home by No. 6 Nevada, UCLA's skid continued with a home loss to Liberty, Santa Clara beat Washington State in Spokane, and Cal fell to Seattle.

Woebegone December for Pac-12 The Pac-12 is enduring the worst nonconference winning percentage in a single December by a major conference in the past 20 seasons. Year Conf. Win Pct. W-L 2018 Pac-12 .514 38-36 2003 Big Ten .605 46-30 2009 Pac-10 .613 38-24 2011 Pac-12 .623 43-26 2012 SEC .628 49-29

Oregon rallied to win at Boise State, Oregon State routed Central Connecticut State and Stanford defeated Long Beach State to lift the Pac-12's record above .500 to 38-36 for the month, with USC still to face UC Davis on Sunday.

Saturday was the third time this season that the Pac-12 has had two days when its teams lost at least five nonconference games. In the previous 20 seasons, that happened only twice.

The previous worst performance by a major conference in the past 20 years came in 2003, when the Big Ten went 46-30 (.605). The Pac-12's previous worst was 38-24 (.613) in 2009, when it was still known as the Pac-10.

Luguentz Dort and Arizona State were stunned by Princeton. AP Photo/Ralph Freso

Princeton's win was the second by the Ivy League over a ranked team this month. Penn beat defending NCAA champion Villanova on Dec. 11, and Arizona State coach Bobby Hurley said the playing field is becoming more equitable.

"There is nothing good that can be taken from this," Hurley said after his team fell to 9-3. "We took a step back. There is a lot of parity in college basketball. If you're not ready to play, you're going to get beat."

UCLA (7-6) has lost four straight games to Belmont, Cincinnati, Ohio State and Liberty by an average margin of 15 points. The Bruins had not dropped four nonconference games in a row since the 2010-11 season.

"This might be one of the most disappointing games I've had," coach Steve Alford said after the Liberty loss. "Trying to reflect back throughout 28 years [as a coach], the word 'disappointment' of just our team and how we performed -- I don't know the last time I was this disappointed in a team. It did not look like us on any level."