At the moment Mark Aguirre was supposed to be standing at center court today, explaining top-ranked De Paul's second-round NCAA tournament victory over St. Joseph's, the 6-foot-7 all-America was bursting through the back door of the University of Dayton arena, his face a mask of anger and frustration.

Standing in Aguirre's place talking to a national television audience was John Smith, a 6-5 senior for St. Joseph's. A man with an 11.2-point scoring average, Smith today was the man who scored the layup that stunned De Paul, 13,458 fans here and a national television audience because it gave the Hawks an astonishing, 49-48 victory in the Mideast Regional game.

Smith's shot, off a pass by Lonnie McFarlan, came with three seconds remaining. It left Aguirre standing helplessly under the basket. His team had no timeouts left and De Paul (27-2) had been upset in its first game of this tournament for the second straight season.

A year ago, the Blue Demons were shocked by UCLA. Today, their tormentor was the same 2,200-student Philadelphia school that only seven days ago had to come from eight points down in the final four minutes to beat American University and qualify for this tournament.

The improbable ending to this improbable game was set up when Skip Dillard, an 85 percent free-throw shooter, missed the first shot in a one-and-one attempt with 12 seconds left.

Bryan Warrick, who had 12 points for the Hawks (24-7), got the rebound to the right of the basket. Clyde Bradshaw and Dillard tried to strip him of the ball at midcourt but he dribbled by both and was met by Aguirre at the top of the key.

Warrick passed to Lonnie McFarlan in the right corner. McFarlan, the 6-foot-5 freshman whose presence in the last 10 minutes keyed St. Joe's comeback from a seven-point deficit, was wide open.

Smith, who had run straight down the court to get into position for a rebound, was shocked to see no De Paul player near him. "I just yelled, 'please ' and Lonnie saw me," Smith said. "No way I've ever made a bigger shot, but I've missed easier ones."

Smith caught the pass under the basket and laid it in with his right hand. Aguirre grabbed the ball as it came through the net and stepped out of bounds to throw it in. He stood there helplessly as time expired in what was undoubtedly the junior's final college game.

"I'm totally speechless," said St. Joe's Coach Jim Lynam, who went back to his alma mater three years ago after coaching three seasons at American U. "Obviously, the biggest win of my coaching career. I feel bad for Coach Meyer. We both know it's much easier in this tournament when you're an underdog."

Smith's shot created an incredible scene on the court. As Lynam was mobbed by his assistnat coaches, Meyer, 67 -- still without a national title after 39 years as a coach -- waited to congratulate him.

As he let go of Meyer's hand, Lynam, 39, saw his wife, Kay, and grabbed her in a hug that seemed to last forever. De Paul's assistant coaches sat on their bench, still not believing it was over.

Aguirre, who scored only eight points -- none in the last 14 minutes (his team did not score in the last 6:25) -- went into the locker room only long enought to don his sweatsuit and radio-earphones. Minutes later, he burst out of the locker room door and headed for the exit.

As several reporters turned to follow, Assistant Coach Ken Sarubbi said, "Don't chase him down. He'll hit someone."

Out the door and through the parking lot went Aguirre, walking back to the hotel, four miles away. He tried to use the earphones to shut out questions. Finally, he stopped and took them off.

"The game is a game," he said. "It just happened that way. That's basketball; nobody can predict it." Then he waved goodbye and kept walking.

"St. Joe's deserved it," Meyer said. "They had the poise in the last two minutes and we panicked when we missed the free throw. We were supposed to be in a man-to-man defense but we double-teamed going for the steal at midcourt and that created a five-on-three for them. But one play doesn't lose a game.We had 40 minutes to win and didn't do it."

The reason they didn't do it was Lynam's ability to control the pace of the game from his bench. The Hawks ran a four-corner offense the entire first half, looking only for layups or wide-open jump shots. They trailed at the half, 27-25.

De Paul looked safe when it led, 42-35, with 10:30 left, thanks to Dillard (12 points) and Bradshaw and Teddy Grubbs (11 each). But Boo Williams, having a miserable, three-for-nine shooting day, picked up his fourth foul and McFarlan replaced him.

From then on, the Hawks were almost flawless. McFarlan scored twice from outside to cut the lead to 42-39 and De Paul started playing almost passively against St. Joe's zone. The Demons still led, 48-43, when Cummings dunked off an Aguirre pass with 6:25 remaining.

Smith made a baseline jumper with 5:58 left to make it 48-45 and De Paul elected to simply hold on.

The clock ran to 2:40 before the teams traded turnovers. De Paul ran it to 1:20 before Warrick stole the ball from Bradshaw. Down came the Hawks. Costner missed a short jumper. Grubbs appeared to have the rebound but he went down and was tied up for a jump ball with 55 seconds left.

Smith won the tap and Warrick swished a 15-footer with 45 seconds left to cut De Paul's lead to 48-47. Thirty three seconds later, Warrick fouled Dillard and Lynam called time.

"We told them to take things one at a time," Lynam said. "Get the rebound first, then get it downcourt for a good shot. We didn't want a timeout because we thought the court would be spread out better without one."

I never thought for a second Skip would miss," Meyer said. "I think the players were thinking the same way."

But Dillard did miss, the ball clanging off the back of the rim and going to Warrick. "When I got to center court, I saw the double-team and I knew if I could get by it, we'd have a chance for a good shot," Warrick said. k"Then I saw Lonnie wide open."