Trojans profit from this margin

All one had to do to assess how unhinged the situation had become in the second half at Gill Coliseum on Saturday afternoon was look at who was coming and going.

Checking in with 11 minutes 18 seconds to play: a second-string USC lineup consisting of walk-on Ryan Wetherell, Kyle Austin, RouSean Cromwell, Abdoulaye N’diaye and Daniel Hackett.

Checking out: dozens of Oregon State fans disillusioned with a game in which the Beavers would trail by as many as 50 points.

Things further degenerated for Oregon State in the final eight minutes, when the Beavers inserted their reserves and an unscheduled junior varsity game broke out.

The Trojans emphatically won the battle of second units as well on their way to a 91-46 victory that was their most lopsided over Oregon State in 116 meetings dating to 1925. The 45-point triumph also represented USC’s biggest margin of victory in a Pacific 10 Conference game since it defeated Arizona State, 117-71, on March 7, 1998.

“It was the easiest game I’ve ever played because they were making every shot,” junior swingman Nick Young said of his teammates after a game in which the Trojans shot 66% from the field.

Senior guard Lodrick Stewart, freshman forward Taj Gibson and N’diaye combined to make 25 of 28 shots, with Stewart making all six of his three-point attempts en route to a game-high 28 points. It was the most three-pointers made by a USC player in a game without a miss.

Stewart said he was inspired by the presence of his father, grandfather and uncle, who sat behind the USC bench. He made six of seven shots and scored 20 points in the first half, which USC (13-4, 3-1) closed with a 16-0 run to take a 49-26 lead.

“He came out hot, so I tried to look for him,” junior guard Gabe Pruitt said of Stewart. “When you have a great shooter like that, you have to try to get him the ball every time you can. He did something with it every time he got it.”

Gibson, who had 20 points on nine-for-11 shooting, scored the Trojans’ first six points of the second half, and it quickly became apparent USC was on its way to a rare breather after its three previous Pac-10 games had come down to the final minute.

Things were going so poorly for the Beavers (8-8, 0-3) early in the second half that when they finally found junior forward Sasa Cuic underneath the basket for an open look, he couldn’t get the ball out of his hands before the shot clock expired.

“It’s hurting. Disappointing. There’s so many negative adjectives I could use,” said Oregon State junior guard Angelo Tsagarakis, the only Beaver to score in double figures with 10 points.

Oregon State Coach Jay John said his team was drained from its intense preparation earlier in the week for top-ranked UCLA, which defeated the Beavers, 71-56, Thursday.

“I don’t feel that guys quit,” said John, whose team shot only 31.5%. “It was one of those days when nothing was working for us and they had tons of things working for them.”

Things such as N’diaye, the big man who had recently fallen out of the rotation but came up big with 16 points and eight rebounds in 19 minutes off the bench. N’diaye made all seven of his shots, including a hook with less than two minutes to play that gave the Trojans an 89-39 lead.

“Guys were hitting shots,” said Pruitt, who watched the final minutes from the bench, savoring the Trojans’ first back-to-back road sweeps of the Oregon schools since the 1970-71 and 1971-72 seasons. “It felt like we couldn’t miss.”

ben.bolch@latimes.com

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UP NEXT FOR USC

Saturday vs. UCLA, Galen Center, 11:30 a.m., FSN Prime Ticket -- In the first crosstown rivalry game in USC’s new $130-million facility, the Trojans will seek to pick up where they left off in the Sports Arena, where they were the last team to defeat UCLA before the Bruins’ run last season to the national championship game. USC will be trying for its fourth consecutive victory in games against ranked opponents in what is expected to be the first sellout at the Galen Center.