LOS ANGELES - Give it up for the Atlantic Sun.

Mercer capped a sensational week for the low-major conference, stunning No. 18 Southern California 96-81 Saturday and spoiling O.J. Mayo’s college debut.

The Atlantic Sun’s dream week began Thursday, when Gardner-Webb shook things up with a 16-point victory over No. 20 Kentucky on the Wildcats’ home court, then Belmont won at Cincinnati on Friday.

“The Kentucky result was on our mind,” USC’s Taj Gibson said. “We knew this was a dangerous team.”

James Florence scored 30 points and the small-school Bears from Macon, Ga., shot nearly 60 percent from the floor in their season-opener.

“There’s no way to describe it,” Florence said.

Watch out Alabama, Harvard and Boston College. Mercer comes your way next.

“They’ll come a lot harder at us,” said Calvin Henry, who added 14 points.

Mayo, one of the nation’s most prized recruits, led the Trojans with 32 points, but he couldn’t help them overcome 19 turnovers and 18-of-32 free-throw shooting.

“It was tough, but they did a great job,” Mayo said. “We need to come out and respect our opponent and play hard. We came out nonchalantly.”

Mercer had the Trojans in trouble early. The Bears shot 59 percent in the first half, when they led by 21 points.

The Bears had five players in double figures, 12 steals, shot 81 percent from the line and outscored USC 14-6 on fast-breaks.

“Coach told us, ‘Hard work beats talent when talent doesn’t work hard,”’ Henry said.

“That was our quote of the week,” Mercer coach Mark Slonaker said.

Mayo worked a lot harder in the second half, and it still wasn’t enough against a more experienced team.

The Trojans opened with a 22-8 run, including 10 by Mayo, who had fans on their feet with a breakaway one-handed layin.

“We felt like they were going to go to him early,” Slonaker said. “We kept telling the guys, ‘Weather the storm and keep attacking.’ You know SC was going to make a run, but we held them off. That shows maturity.”

He whipped a behind-the-head pass to Gibson, who missed on the drive, but Gibson dunked on USC’s next possession to get them to 55-52.

Gibson finished with 13 points and 14 rebounds. Angelo Johnson had 17 points for the Trojans, who won a school-record 25 games and reached the final 16 of last season’s NCAA tournament.

“We got tired and couldn’t sustain any effort for any long period of time,” coach Tim Floyd said. “The 47 points we gave up in both halves was very discouraging. That is somewhat reflecting of what we have been experiencing in practice. We are a team of two juniors and three sophomores who played a year ago. Our freshmen are not ready yet.”

Mercer answered USC’s run with six straight points and soon restored its lead to double digits on a 3-pointer by Brian Mills.

Mayo came up with three 3-pointers in the final three minutes, but the game was already out of reach.

“As good as described,” Henry said about Mayo. “They ran every play and screen for him. He made us work for it.”

USC fell to 0-3 in season openers under Floyd. They lost the two previous years in overtime to Cal State Northridge and South Carolina.

“Tim is going to get this team going,” Slonaker said. “It’s just early.”

The Trojans won’t play their lone exhibition game until Dec. 8, so they jumped into the regular season without playing anybody but each other in practice.

Mike Ehrmann / Getty Images The Week in Sports Pictures The nation grieved for those hurt, killed and affected by the Boston Marathon bombings. After one of the suspects was caught on Friday — following a day-long lockdown and manhunt — sports returned to Boston over the weekend.

It showed. USC shot 29 percent in the first half and missed a slew of open shots. Mayo committed four of his team’s nine turnovers in the half.

“We missed a lot of easy shots and a ton of free throws,” he said. “It hurts us. We got to learn from this and get better.”

Mayo wore No. 32 in tribute to his favorite childhood player Magic Johnson; it’s also the number O.J. Simpson wore as a Heisman Trophy-winning running back for the Trojans.

In a look reminiscent of Kobe Bryant, another of his favorites, Mayo wore black sleeves on both arms and both legs.

Hearing his name announced for the first time as a college player “was a lot of fun. I wish we would’ve won,” Mayo said.

USC played without guard Daniel Hackett, who has a broken jaw but will return to practice on Monday, and freshman Mamadou Diarra, who had hernia surgery.