Anthony Brown scored 15 points, Marcus Allen added a career-high 13 points and Stanford lost at No. 11 Utah, 75-59, on Thursday night.
The Cardinal (7-5 in the Pac-12, 16-8 overall) plays at Colorado on Sunday at 1 p.m. Stanford is currently in a three-way tie for fourth place, a game behind Oregon and three games behind co-leaders Utah and Arizona.
California, which beat the Buffaloes, is a game behind Stanford.
Chasson Randle, the Pac-12's top scorer, went scoreless in the first half and hit his first basket over 13 minutes into the second half. He finished with 10 points on 2 of 11 shooting and missed four long-range shots.
Rosco Allen, one of Stanford's top rebounders, did not make the trip with a back injury. Michael Humphrey made the start in his place and was an early presence inside. He wasn't able to stay in the game very long due to foul trouble.
Stanford went over seven minutes, spanning both halves, without making a field goal. By the time Nastic hit a jumper just over five minutes into the second half, the Utes had built a 19-point advantage.
Utah outscored the Cardinal 20-2 over those seven minutes. Stanford stuck around but never seriously threatened the lead the rest of the way.
Brown hit a 3-pointer with 2:12 remaining in the first half to tie the game at 27. Utah scored the final six points to take a 33-27 halftime advantage.