Dior Lowhorn hit consecutive 3-pointers in overtime and scored 22 points, leading San Francisco to an 81-77 upset of No. 13 Gonzaga on Saturday night.
Matt Bouldin scored Gonzaga's only three baskets in the extra session and the Bulldogs (17-4, 6-1 West Coast Conference) lost for the first time in 28 regular-season WCC games.
Angelo Caloiaro made a 3 with 32.8 seconds left that helped the Dons end a nine-game skid in the series.
Many in the raucous, near-capacity crowd of 4,114 at Memorial Gym rushed from the stands after the final buzzer. Fans and USF players danced on the court for several minutes in a wild celebration until police and security put an end to the frenzy.
Lowhorn went 5 of 7 on 3-pointers after coming in 8 for 47 from long range this season, sending the Dons (8-14, 3-4) to their first win over Gonzaga since a 73-70 victory on Jan. 20, 2005.
Lowhorn hit a tying 3-pointer with 9.8 seconds left in regulation after a miss moments earlier and Steven Gray missed a 3 on the other end. Kwame Vaughn's 70-foot prayer for USF bounced out off the backboard and rim at the buzzer.
Rashad Green, moved into the starting lineup by USF coach Rex Walters to shake things up, scored 15 points and Caloiaro had 11 with three 3s. USF ended a three-game losing streak.
Gray missed two free throws in OT for the Zags after making two with 25.3 seconds left in regulation.
Bouldin finished with 15 points, standout Zags freshman Elias Harris scored 21 points and Robert Sacre added 19.
Gonzaga had won nine straight overall and 22 in a row against league opponents. The Zags had to rally from 14 points down in the second half of their 71-64 win at Santa Clara on Thursday night and then faced another tough one on the Hilltop.
The teams traded big plays down the stretch in regulation. After Lowhorn and Dontae Bryant knocked down back-to-back 3-pointers to give USF a 60-57 lead with 4:41 to play, Bouldin swished a 3 from the right wing moments later.
Lowhorn, the WCC's leading scorer the last two seasons, tied it at 48 with his driving baseline scoop shot with 10:22 to go. Caloiaro put USF ahead the next time down with a 3-pointer.
Lowhorn overcame early foul trouble. He was whistled for his third foul with 2:28 left in the first half and took a seat.
After Demetri Goodson's 3-pointer with 17:03 left gave Gonzaga its biggest lead at 42-32, USF answered with a 9-0 run to get right back in it. Caloiaro knocked down a 3 at 14:56 to make it 42-41 and Gonzaga went 3:15 without scoring.
The Bulldogs conclude the conference season with five of their final seven games at home in Spokane, Wash. They are picked to win their 10th straight WCC regular-season crown.
After Gonzaga hosts Portland on Thursday, the Zags hit the road for a key non-conference game at Memphis next Saturday.
The Dons were outrebounded for only the fourth time in their last 16 games, 39-34.
Both teams were clicking offensively early before cooling off late in the first half. Gonzaga shot 48.4 percent on the way to a 33-26 lead at the break. While the Zags led by as many as nine, there were four ties and five lead changes in the opening 20 minutes.
(This version SUBS 5th graf to correct date, based on Gonzaga's records; RESTORES previous)
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