Los Angeles ? As if Southern California wasn’t playing well enough already, its backups came in and didn’t let up.

Playing at a frenetic pace, the 22nd-ranked Trojans built a 23-point lead in the first half and never looked back, beating No. 16 Stanford 103-78 Thursday night in the first round of the Pacific-10 tournament.

“It’s probably one of the best offensive games we’ve played all year,” USC coach Henry Bibby said.

The Trojans shot 55 percent from the floor and 76 percent from the foul line. It was USC’s third victory over the Cardinal (19-9) this season.

Pac-10 player of the year Sam Clancy led five USC players in double figures with 25 points. Brandon Granville added 20 points and 11 assists, and David Bluthenthal scored 17 points.

After USC starting guard Errick Craven got in foul trouble in the first half, the Trojans didn’t miss a beat. Jerry Dupree came in and scored 10 points. Desmon Farmer also came off the bench and finished with 19 points.

The fourth-seeded Trojans (21-8) will play top-seeded Oregon (23-7) in today’s semifinals at Staples Center.

No. 5 Cincinnati 79, South Florida 57

Cincinnati Steve Logan scored 15 points in a brief appearance as Cincinnati moved into the semifinals of the Conference USA tournament. The Bearcats (28-3) have won all seven of the conference’s regular-season titles.

South Florida (19-12) fell behind by 29 in the first half, its biggest deficit of the season, and never got closer than 18 the rest of the way even though Cincinnati rested its regulars for most of the second half.

Altron Jackson, the conference’s career scoring leader with 1,987 points, rarely got an open shot against the Bearcats’ switching man-to-man defense. He missed his first four shots and finished with 21 points.

No. 7 Pittsburgh 76, Boston College 62

New York Donatas Zavackas scored 16 points, and Chevon Troutman added 15 for the Panthers (26-4), who took control with a 21-4 surge over the final six minutes of the first half in the Big East Conference quarterfinals. Boston College (20-11), which defeated Pittsburgh for the Big East tournament title a year ago, is in jeopardy of missing the NCAAs.

No. 9 Oregon 86, Washington 64

Los Angeles Luke Jackson scored 16 of his 27 points after halftime, and Oregon beat Washington in the first Pacific-10 Conference tournament game in 12 years. The win was Oregon’s sixth straight and gave the top-seeded Ducks (23-7) their most victories in a season since 1945. Doug Wrenn led the eighth-seeded Huskies (11-18) with 14 points and seven rebounds, but had only two points in the final 251/2 minutes.

No. 11 Florida 81, Auburn 63

Atlanta Udonis Haslem had 22 points and 10 rebounds, and Brett Nelson hit six three-pointers as Florida beat Auburn in the first round of the Southeastern Conference tournament. The Gators (22-7) play Mississippi State in today’s quarterfinals. They’ll need to win four games in four days to take their first SEC tournament title.

Nelson had 23 points and four assists, shooting 6-of-11 on three-pointers. Haslem was 7-of-7 from the floor and 8-of-8 from the free-throw line against Auburn’s short-handed and undersized frontcourt before fouling out with 2:11 left.

Haslem also had three assists and two blocked shots.

No. 13 Marquette 84, Louisville 76

Cincinnati Cordell Henry scored 24 points and repeatedly darted through Louisville’s intense full-court pressure for soft jumpers, steadying Marquette (25-5) in the Conference USA quarterfinals.

Louisville (18-12) erased most of an 18-point deficit by going to its press, but still lost to the Golden Eagles for the third time this season. Reece Gaines scored 29 points for the Cardinals.

No. 15 Arizona 73, Arizona State 56

Los Angeles Luke Walton had 25 points and eight rebounds as the Wildcats beat archrival Arizona State in the opening round of the Pac-10 tournament. The second-seeded Wildcats (20-9) meet the winner of Thursday’s late UCLA-California game in tonight’s second semifinal matchup.

Jason Gardner added 22 points Arizona. Jason Braxton scored 12 points for seventh-seeded ASU (14-14), which finished its season by facing six straight ranked teams. The Sun Devils were 1-5 during the stretch, beating only UCLA on Feb. 16. ASU made only 2 of 12 foul shots.

No. 19 Connecticut 72, Villanova 70

New York Freshman Ben Gordon scored a season-high 23 points, including the winning three-pointer with 11.8 seconds to play in the Big East quarterfinals. The Huskies (22-6) won their seventh straight.

No. 20 Miami 84, Georgetown 76, OT

New York Marcus Barnes scored five of his career-high 27 points in overtime, and Miami reached the Big East semifinals for the third time in four years. The Hurricanes (24-6) will play Pittsburgh today for a berth in the title game. The loss dealt a severe blow to Georgetown’s chances of receiving an NCAA bid. The Hoyas are 19-11.

No. 24 Xavier 65, UMass 59, OT

Philadelphia Romain Sato scored 21 points, and Xavier overcame a tying shot at the end of regulation in the Atlantic 10 quarterfinals. Eric Williams, a backup forward for Massachusetts (14-16), heaved in a three-pointer from 24 feet away with 0.7 seconds left to tie it at 52. David West scored eight of his 14 points in overtime for Xavier (23-5).