ST. LOUIS » Reality hit Middle Tennessee State guard Jaqawn Raymond as he walked triumphantly off the floor. Giddy Potts thought it might come later, once he returned to the team hotel and flipped on the TV.

It sunk in immediately for Michigan State.

Relying on the same balanced scoring that carried them to the NCAA Tournament, the No. 15 seed Blue Raiders ended the second-seeded Spartans’ title hopes in convincing fashion today. They never trailed in a 90-81 first-round victory that sent brackets around the country into trash cans.

“We wanted to win this game as bad as anybody wanted us to win,” said Potts, the Blue Raiders’ hot-shooting sophomore guard. “We played our (butts) off today.”

Reggie Upshaw had 21 points and Potts finished with 19 for Middle Tennessee State (25-9), which became the eighth No. 15 seed to knock off a No. 2 since seeding began in 1985. The last time it happened was 2013, when Florida Gulf Coast beat Georgetown on its way to the Sweet 16.

The Blue Raiders will try to do the same against No. 10 seed Syracuse on Sunday.

“I’ll be honest with you, in my wildest dreams I didn’t think they’d hit some of the shots they hit,” Michigan State coach Tom Izzo said. “We didn’t guard them good, but man, they made some shots.”

The Spartans (29-6) were a trendy pick to win the national championship after capturing the Big Ten’s regular-season and tournament titles. Part of it had to do with the experience of Valentine and the seniors, and part of it had to do with Izzo’s postseason pedigree.

“I’m more mad and disappointed because I know what this team could accomplish,” Valentine said. “It kind of fell apart, and it just stinks right now because I know the capability our team had.”

The Spartans’ Matt Costello matched a career-best with 22 points, but it wasn’t enough to offset Valentine’s miserable afternoon. The senior had 13 points and 12 assists, but he also had six turnovers — one of them coming with the Spartans trailing 79-76 and less than three minutes to go.

Michigan State twice had chances to tie the game after that, but Valentine missed an open 3 from the top of the key, and Bryn Forbes missed another. The Blue Raiders eventually scored on back-to-back runouts to establish some breathing room, then coaxed the final few seconds off the clock.

Darnell Harris and Perrin Buford scored 15 apiece, and Raymond had 11, as the Conference USA champion Blue Raiders won their first NCAA Tournament game since 1989.

Not that they haven’t made a statement before: They beat Kentucky in the first round in 1982.

They never seemed intimidated by the Spartans, roaring to a 15-2 lead in the opening minutes and slowly getting the Syracuse and Dayton fans in the building on their side.

Michigan State chipped away at its deficit but never managed to make an extended run. Valentine was saddled with two fouls and rendered ineffective most of the way, and the backcourt of Forbes and Eron Harris combined for four turnovers while managing a single point.

Valentine’s frustration reached its apex after he committed back-to-back turnovers in the second half. With the Blue Raiders leading 51-43, Valentine stalked back to the huddle and slammed his hand into the floor.

Michigan State slowly trimmed the lead to 65-64 on a basket by Costello with eight minutes to play, but the Blue Raiders scored on their next six trips down floor.

It was the first time the Spartans, heavily favored to reach the Final Four, lost in the first round since 2011.

“We just couldn’t make that one play,” the Spartans’ Tum Tum Nairn said. “That’s the thing about this tournament — tomorrow is not a guarantee.”

SENIOR SEND-OFF

It was the final game for Valentine, Costello, Forbes and backup forward Colby Wollenman, and Izzo got emotional talking about the impact they had on his program. “They’ve done it all,” he said. “Other teams are going to hear … what this team did. That’s probably the best compliment you can give them.”

TIP-INS

Middle Tennessee State: The Blue Raiders have won seven straight. … Potts, who led the nation in 3-point field-goal percentage, was 3 for 5 from beyond the arc. … Upshaw was 8 of 14 from the field.

Michigan State: Forbes finished with 14 points. Harris had nine points and five turnovers. … The Spartans reached the national title game the last time they were No. 2 seeds, winning the championship in 1979 and finishing second in 2009. … The Spartans had won 13 of their last 14.

UP NEXT

Middle Tennessee State plays the Orange on Sunday.