OMAHA, Neb. — Missouri coach Frank Haith implored his team not to overlook Norfolk State. He spent all week trying to prove to his players that the Spartans were better than a No. 15 seed.

Nothing seemed to stick.

"You don't see them on TV. The guys don't know their players," Haith said. "You worry they don't understand, hey, these guys are pretty doggone good."

They wound up finding out just how good.

By that time, it had cost them dearly.

Kyle O'Quinn had 26 points and 14 rebounds in a breakout performance, and the plucky MEAC champions upset the second-seeded Tigers 86-84 on Friday, advancing in the West Regional while Missouri headed home to ponder what could have been.

"We tried all week, our coaching staff, explaining how good Norfolk State is," Haith said quietly. "You get in the NCAA tournament on a neutral court, they cheer for the underdogs. That's what happens. And they stay in the game, they bank in a couple 3s, you have a ballgame."

Missouri struggled with the Spartans (26-9) all afternoon, falling behind by eight in the opening minutes and by six late in the second half. But the Tigers still had a final shot when O'Quinn missed two free throws with 3.8 seconds left.

Haith called timeout to set up a final play, and the ball wound up in Phil Pressey's hands. He took a couple of hard dribbles and let loose a 3-pointer from the wing that clanked off the back iron and fell to the floor as the buzzer sounded.

Pressey walked over to a courtside table, his face buried in his jersey, before falling to the floor in disbelief as Norfolk State players dashed to center court to celebrate.

"We had great execution there on that last play," Haith said. "He got a good look."

But it didn't go in, and all those brackets that had the Big 12 tournament champs advancing to face Florida in the West Regional — perhaps all the way to the Final Four — can be torn up.

"We messed up some brackets! We messed up some brackets!" O'Quinn said as he led his team to the locker room. "We even messed up my bracket."

Michael Dixon led Missouri (30-5) with 22 points, and Pressey and fellow guard Marcus Denmon finished with 20 each. Pressey also contributed eight assists, though senior guard Kim English was held to two points on 1-for-7 shooting.

"It was a tough loss for us. We had higher expectations for ourselves, and there's really nothing to say when you come out and don't perform," Denmon said.

Pendarvis Williams and Chris McEachin each added 20 points for the Spartans, who have already made their first trip to the NCAA tournament a memorable one. They became the fifth No. 15 seed to beat a No. 2 and the first since fellow conference member Hampton knocked off Iowa State in 2001.

"You always go into the game with a sense of confidence," O'Quinn said, "but I never thought it was an upset-alert until that buzzer went off.

"At the end of the game," he said, "that's when I thought it would happen."

The Tigers rolled into the NCAAs on the strength of a dominant run to the Big 12 tournament title, rarely getting tested in three games in Kansas City. That was enough to make Missouri a trendy Final Four pick, something the school had never before accomplished.

Norfolk State made sure it wouldn't happen this year, either.

The plucky Spartans shot 54.2 percent from the field — 62.5 percent in the second half — and managed to knock down 10 of 19 3-point shots. They also turned the ball over just 11 times against the Tigers' quick-handed guards, who had caused fits for most teams this season.

"We knew coming into this game if we let them hang around it was going to be a ballgame. They hung around the whole game," Pressey said. "They made the plays at the right time."

Missouri knew right away that Norfolk State wasn't going away easily.

The Spartans opened the game on 15-7 surge, turning most of the folks dressed in Florida blue and Virginia orange into surrogate fans. And when Missouri jumped ahead on the strength of three consecutive 3-pointers, Norfolk State didn't seem to be rattled.

Fifth-year coach Anthony Evans simply called timeout and Norfolk State regrouped.

Things were going so well for the Spartans in the first half that O'Quinn, an 18-percent shooter from beyond the arc, swished one from the top of the key. The big guy added a conventional three-point play later in the half, slamming his hand onto the court after he was fouled and then stepping to the free throw line and giving Norfolk State a 38-36 lead.

Dixon's basket with 23.4 seconds left meant a tie game at halftime.

Missouri spent nearly the entire 20-minute break in its locker room. The Spartans were back on the court before it was half over, putting up shots like it was a Sunday afternoon shootaround.

They must have liked the way things were going.

The game was tied 81-all when O'Quinn grabbed an airball and put it back with 34.9 seconds left, getting fouled in the process. The three-point play made it 84-81.

O'Quinn added the first of two free throws moments later, but Pressey hit a deep 3-pointer from the wing with just a shade over 10 seconds left, giving Missouri Gov. Jay Nixon — seated two rows behind the Tigers' bench — some reason to hope.

Rodney McCauley restored an 86-84 lead with the first of two free throws, and after a loose ball wound up in Norfolk State's hands, O'Quinn missed both of his foul shots.

That set the stage for Missouri's dramatic final possession.

A possession that nobody at tiny Norfolk State will ever forget.

"Coming into the game, I believed it. I believed it from the jump. Honest to God's truth," McCauley said. "We've got good shooters. We dig deep. We're not ready to go home yet. We've got five seniors. We're ready to keep playing."