PROVIDENCE, R.I. - Richmond was on the wrong side of an NCAA tournament upset this time, and Saint Mary’s is moving on for the first time in more than 50 years.

Omar Samhan had 29 points and 12 rebounds despite spending most of the game in foul trouble, and Saint Mary’s pulled away from Richmond to win 80-71 on Thursday in the first round of the South Regional.

“They didn’t have a matchup for Samhan,” said Saint Mary’s coach Randy Bennett, who brought the school its first NCAA victory in six tries since 1959. “All year long, when people don’t have a matchup for him, our guards are good enough passers, smart enough players — they’ll make you pay if you don’t have a guy out there that can guard him.”

The 10th-seeded Gaels (27-5) will play Saturday against Villanova, a No. 2 seed that escaped from the first round with a 73-70 overtime victory over Robert Morris.

Mickey McConnell, the West Coast Conference tournament MVP when the Gaels upset Gonzaga in the title game, scored 23 points for Saint Mary’s. Thanks in large part to Samhan, the Gaels held a 40-18 rebounding edge, outrebounding Richmond 19-13 under their own basket for a 21-4 advantage in second-chance points.

“Once he got warm, he ran with it and went on a tear,” Richmond forward Darius Garrett said. “You can’t let a player like that get comfortable.”

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David Gonzalvez scored 18 and Kevin Anderson 16 for Richmond (26-9). The Spiders, who lost to Temple in the Atlantic 10 tournament championship game, have been known as a giant-killer, with a rich NCAA history of knocking off defending champions (Indiana in 1988) and future NBA Hall of Famers (Charles Barkley’s Auburn team in ’84).

The Spiders have won NCAA tournament games as No. 12, 13, 14 and 15 seeds. But playing as a favorite this year for the first time in school history, they failed to make it out of the first round.

“We couldn’t guard Omar,” Richmond coach Chris Mooney said. “Our inability to guard him led to other troubles.”

Samhan scored the Gaels’ first 10 points, but he picked up his first foul 5 minutes into the game and his second midway through the first half. Richmond led 19-17 at the time, and Bennett didn’t give much thought to sitting Samhan down.

“If you have a guy like Samhan, why would you sit him when he only has two?” Bennett said. “I haven’t been a big believer of that. It depends on how smart your player is. Omar is a key player to us. He was tonight. The more minutes we can have him out on the floor, no question he’s better for us.”

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Samhan picked up his third foul with 6:31 left in the first, and went to the bench for the rest of the half with 17 points and seven rebounds. He had 27 and 11 when he picked up his fourth foul with 9:13 left and Saint Mary’s leading 59-50; he sat down and didn’t return for six minutes.