Bennie Boatwright added 13 points for the sixth-seeded Trojans, who rallied from 10 points down in the first half and then withstood a sloppy finish in advancing to play No. 3 UCLAnight.
David Crisp had 22 points, eight rebounds and seven assists for the Huskies (9-22) but missed a game-tying 3-point attempt in the closing seconds. Noah Dickerson scored 18 points, but Washington was undone by 10 second-half turnovers in its school-record 13th straight loss.
USC (24-8) likely needed a win to stay in NCAA Tournament contention, but the Trojans struggled much of the night, not putting it away until Shaqquan Aaron hit two free throws with 3 seconds left.
Washington came out hot in the teams' second meeting, with Matisse Thybulle hitting three straight 3-pointers to put the 11th-seeded Huskies up 37-27.
But USC switching to a zone and Metu's play inside fueled a 10-2 run to close the half. The Trojans took their first lead early in the second half on consecutive dunks by Metu.
Things unraveled for the Huskies from there. Malik Dime had to leave briefly with an apparent finger injury after blocking a shot. Then a foul and ensuing technical foul on Carlos Johnson led to Boatwright hitting four straight free throws and USC soon led by 14.
USC missed three late free throws to help Washington get within 76-73 with 22 seconds left.