COLUMBIA — The 77,000-plus fans at Williams-Brice Stadium had roared in celebration for most of Saturday night, and they were doing it again with 1:44 left in the first half, as Connor Shaw lofted a perfect 20-yard completion to Bruce Ellington that put the Gamecocks two yards away from Alabama-Birmingham’s end zone.

But then every eye in the place shifted toward the 25-yard line, where Shaw writhed in pain on the grass. Trainers and USC coach Steve Spurrier rushed out to see him. The fans fell silent. Shaw eventually got up and walked off the field with his right arm pinned against his side.

It was similar to the sobering image from USC’s Aug. 30 season opener at Vanderbilt, where Shaw initially injured his right (throwing) shoulder. He returned that night because USC needed him. The eighth-ranked Gamecocks did not need him Saturday, when Shaw stayed on the sideline and Dylan Thompson took over, polishing off a 49-6 win over UAB.

Thompson acquitted himself well again, completing 5 of 10 passes for 177 yards and two touchdowns. He dissected a hapless Conference USA defense, just as he did last week against East Carolina, when he played the entire game in Shaw’s place. For the second straight game Saturday, USC (3-0) reached 500 yards (501 against UAB), marking just its fifth 500-yard game since the start of 2007.

The fans who stayed until the end Saturday cheered coach Steve Spurrier’s 200th career victory as a college head coach — the 22nd-most in Bowl Subdivision history. But the celebration was tempered by the anxiousness about Shaw’s status for next Saturday’s 3:30 p.m. game against Missouri — the beginning of the heart of USC’s Southeastern Conference schedule.

Shaw said he aggravated his shoulder blade, which he said has a “crack” as a result of the hit at Vanderbilt. Saturday, he got hit on the same spot. Before leaving, he was 8 of 14 for 107 yards, a touchdown and an interception. Spurrier said Shaw suffered “no extra fracture” Saturday.

“The pain was pretty up there,” Shaw said after the game. “It’s a little tight right now. I got better in five days, more than I expected, last week (before the UAB game), so hopefully I’ll be back next week. I felt good coming into today. The more and more I threw (against UAB), the more and more it hurt a little bit. But I absolutely thought I could play coming into this game.”

The crowd’s mood was happier before the game, when Shaw’s image appeared on the new video screen and he was announced as the starting quarterback. It was uncertain before the game whether Shaw or Thompson would start, and when Shaw’s face popped up, the fans cheered.

Spurrier said USC’s medical staff had cleared Shaw, but Spurrier still asked Shaw before the game, “If you get hit on that (spot), are you going to be hurting?”

“No, I’m going to be all right,” Spurrier recalled Shaw saying.

“I thought he deserved and earned the chance to start,” Spurrier said. “He struggled a bit early there. He seemed a little tentative on some throws, a little hesitant. But maybe they had everybody covered. I don’t know. It’ll be interesting to watch the tape of this game. He didn’t practice much last week. Maybe that was a reason he might have been a little tentative.”

What matters more than the tape of a blowout is how Shaw responds to treatment this week. A victory over Missouri is far from guaranteed, even if Shaw plays. And despite Thompson’s confidence-building success in these past two games, neither opponent’s defense in any way resembles an SEC outfit.

“I think going into next week’s game, the biggest thing for a lot of players is nerves and worrying,” Thompson said. He believes he worked out his nerves against ECU and UAB.

If USC can beat Missouri, it almost certainly will be 5-0 heading into the Oct. 6 home game against Georgia, which could end up being the de facto SEC East Division championship. (After Missouri, USC travels to SEC doormat Kentucky.)

Spurrier knows Shaw’s experience gives him the best chance against Missouri, and emphasized that if Shaw is 100 percent, he is the starter. Whether he will be either is once again uncertain.

“If we need to use two quarterbacks at times, Dylan can make some throws,” Spurrier said. “He’s proven that the last two weeks. But Connor’s played too well for us to think we’ve got any issues here now. Hopefully he can get that shoulder well, but if he gets hit and goes down like that, it’s not right to put him out there.”