GREENVILLE, S.C. — After 15th-seeded St. Peter’s stunned No. 2 Kentucky in Thursday’s slate of games, it briefly looked as if the run of March upsets might extend into a Friday afternoon matchup between No. 2-seeded Auburn and No. 15-seeded Jacksonville State.

But the Tigers held off the Gamecocks, 80-61, in the first round to advance to face the winner of a game between Southern California and Miami.

The Gamecocks earned a trip to the N.C.A.A. tournament despite losing to Bellarmine in the Atlantic Sun tournament, because Bellarmine is not eligible for the national tournament as its athletic program transitions to Division I.

Jacksonville State took an early lead with stellar 3-point shooting and 15 early points from guard Jalen Gibbs, who finished with 20 points. But the underdogs’ control of the game was short-lived, and by the second half, Jacksonville State’s lead was a distant memory.

Auburn went on an 11-0 run in the final three minutes of the first half to take a 39-27 lead to the break. The Tigers did it by tightening up their defense, anchored by the 7-foot-1 forward/center Walker Kessler, a finalist for the Naismith Men’s Defensive Player of the Year award. The tough shots that Jacksonville State knocked down early in the game no longer fell.

Auburn’s run ballooned to 18-0 early in the second half. Jabari Smith, a potential lottery pick in the N.B.A. draft, knocked down a 3-pointer in transition, and the double-digit hole was too deep for the Gamecocks to climb out of. Smith threw down a thunderous dunk over a Jacksonville State defender in the final minutes of the game, after which he could be seen nodding his head and mouthing the words, “I got up.” The play wowed the crowd in Greenville, S.C., and his teammates celebrated with glee. He finished with 20 points and 14 rebounds.

Auburn looked like the best team in the nation during a 19-game winning streak that lasted from November through February. Smith, a highly touted 6-foot-10 freshman, led the way, averaging 17.1 points and influencing games both with offense and defense. He was named the Southeastern Conference freshman of the year.

Despite struggles down the stretch, particularly in guard play, which led to losses to Florida and Tennessee late in the regular season and a loss to Texas A&M in the SEC tournament quarterfinals, the Tigers earned a No. 2 seed in the tournament. Many still believe that this team has the size and shooting that could carry it to the Final Four, and potentially, its first national championship win under its eight-year coach, Bruce Pearl.

No deep run this year for Loyola-Chicago.

Loyola-Chicago will not have a starry, No. 1-seed-toppling N.C.A.A. tournament run this year. Ohio State — or maybe it was just Loyola’s shooting — made certain of that on Friday.

Ohio State, which had stumbled in the second round of the Big Ten Conference tournament, barged past Loyola, 54-41, in Pittsburgh. E.J. Liddell, a 6-foot-7 forward from Belleville, Ill., accounted for more than a quarter of Ohio State’s points, with 16.

Malaki Branham, a freshman guard, added 14 more for Ohio State, which will play on Sunday and try to advance to the round of 16 for the first time in nine years.

The outing was among Ohio State’s worst offensive performances during a season when it has scored at least 80 points in 11 games, prompting a postgame cross of a grimace and a chuckle from Coach Chris Holtmann. The Buckeyes defense, though, allowed Loyola to make just 27 percent of its field goal attempts. The Ramblers also sank only three free throws.

“We could hang our hat on our defense right now,” Holtmann said, “and we did that.”

Braden Norris, who finished with 14 points, was the lone Rambler to score more than 8, and Lucas Williamson, a sterling defender who also led Loyola in scoring this season, managed to make just a free throw and a 3-pointer. He missed nine of his 10 shots from the field.

“I’m disappointed in myself,” Williamson said. “I don’t feel like I played to the standard that I put myself at.”

He was, he added, “kind of just stunned right now.”

Although Loyola struck first, Ohio State controlled the game for close to its entirety: The Buckeyes trailed for just more than two minutes all afternoon.

The loss gave Loyola, which pummeled a No. 1 seed last year, its earliest exit from the N.C.A.A. tournament since 1968, when the field included just 23 teams. In their three subsequent berths — in 1985, 2018 and 2021 — the Ramblers reached at least the round of 16, with a Final Four appearance in 2018.

Alanis Thames reported from Greenville, and Alan Blinder from Atlanta.