Wes Clark scored 25 points, Jeremy Harris added 23 and No. 13 seed Buffalo pulled off the biggest upset of the NCAA Tournament’s opening round, rolling over No. 4 seed Arizona 89-68 in the South Region on Thursday night.

The smaller Bulls (27-8) used their quickness to zip around the Wildcats (27-8), scoring at the rim and on kickout 3-pointers.

Defensively, Buffalo neutralized Arizona’s size inside by collapsing on the paint, forcing the Wildcats to shoot from the perimeter. Arizona went 2 for 18 from beyond the 3-point arc, while the Bulls knocked down 15 of 30. Get Pac-12 Conference news in your inbox with the Pac-12 Hotline newsletter Sign Up

CJ Massinburg had 19 points and Buffalo shredded Arizona’s defense at a 55-percent clip for the program’s first NCAA Tournament win.

The Bulls move on to face Kentucky in Saturday’s round of 32.

Dusan Ristic had 16 points, and Deandre Ayton finished with 14 points and 13 rebounds to lead Arizona.

Arizona has played through one of the most difficult seasons in program history. The Wildcats were twice entangled in a federal investigation into nefarious recruiting practices and lost one of their best players twice to injury. Trier missed two games after testing positive for the same banned substance that cost him 19 games a year ago.

Outside of an 0-for-3 trip to the Bahamas, their focus on the court rarely wavered. Arizona won the Pac-12 regular-season title and routed Southern California in the tournament title game, becoming the second team in conference history to sweep both in consecutive seasons.

The Wildcats were the No. 4 seed in the South, but Buffalo was not an easy opening game for the Wildcats.

The Bulls are fast, play up-tempo and shoot the 3 — areas the Wildcats have struggled against.

Arizona had trouble keeping up with the quicker Bulls early and had trouble getting the ball inside to Ayton. Harris and Clark used their quickness to combine for 27 first-half points, and the Wildcats went 1 for 8 from 3-point range to trail Buffalo 40-38.

Buffalo used a similar blueprint to build a 65-55 lead midway through the second half. Massinburg banked in a 3-pointer to stretch the lead to 13 and the Bulls kept building it, racing off to the program’s biggest victory.

Arizona’s surprise loss to Buffalo means the Pac-12 is now Pac-done.

It’s the first time since 1986 that the conference has gone winless in the NCAA Tournament. Arizona, Utah and Washington all lost their opening games that year.

It’s a disappointing end for the conference that only put three teams in the field and lost UCLA and Arizona State in the First Four in Dayton.

Less than 10 percent of fans with brackets in ESPN and Yahoo games selected Buffalo to win. About 5 percent picked Arizona as the national champion.

BIG PICTURE

Arizona will be in rebuilding mode this offseason with Ayton, Trier and Rawle Alkins headed to the NBA and a thin recruiting class so far.

Buffalo picked up the program’s biggest win with its best game of the season.

UP NEXT

Buffalo will face Kentucky in the round of 32 on Saturday.