ATLANTIC CITY, N.J., JUNE 16 -- Michael Spinks fought as he does each of his fights, "with all my heart and guts." What's more, he fought more aggressively than usual.

Gerry Cooney, by his own admission, choked. "I was very tight going into the fight," Cooney said this morning. "I felt I couldn't catch my breath, I couldn't take a deep breath and get going. I felt like I was a step behind the whole night. Everybody handles pressure differently."

Cooney came unraveled in what seemed a classic case of prefight nerves. "I was just very tight. I felt tight the last few days. I couldn't relax. I'd try to relax, but I couldn't get relaxed and I felt very tight. I felt I couldn't get a deep breath."

The result was practically as decisive as a fight can be. By knocking down Cooney twice and finally stopping him at 2:51 of the fifth round Monday night, Spinks set up a showdown with Mike Tyson, probably in 1988. Further, Spinks left Cooney clearly with no future in boxing although Cooney professed today not to know his plans.

"I want Tyson," Spinks' manager, Butch Lewis, proclaimed as loudly as his almost-lost voice would let him. "Next week, I'm going to make the calls, set up the meetings. You've read we're afraid to fight Tyson. That's definitely not the case. You can take it out of the headlines, that we don't want to fight Tyson. We're running to him now."

That inevitable confrontation between the two undefeated heavyweights -- Spinks, 30, is 31-0; Tyson, 20, is 30-0 -- will have to wait until next year, according to Jim Jacobs, Tyson's comanager. Tyson's schedule is full this year.

Tyson, who holds the World Boxing Association and World Boxing Council titles, is an overwhelming favorite to win the third and last version of the heavyweight title when he fights International Boxing Federation champion Tony Tucker Aug. 1. Spinks recently was stripped of the IBF title for fighting Cooney instead of an IBF-named opponent. Tyson then is scheduled to fight Tyrell Biggs in October. But Tyson-Spinks will happen.

"Michael is courageous, he has heart," Tyson's trainer, Kevin Rooney, said of Spinks immediately after Spinks had cut down to size the 6-foot-7, 238-pound Cooney. "But I still think Mike will go in there and eat him up."

But surely Tyson must now regard Spinks in a new light. Against Cooney, Spinks, at 208 3/4 the heaviest he has been, was far more aggressive than he ever had been in a major fight. In his three previous big bouts -- two against Larry Holmes to win and defend the IBF heavyweight title, and one against Dwight Muhammad Qawi to unify the light-heavyweight titles -- Spinks won 15-round decisions. But against Cooney, Spinks was more offense-minded.

"I had been trying to be aggressive in training," said Spinks, "so it was hard for me to back up in the fight."

Eddie Futch, Spinks' 75-year-old trainer who trained Holmes when he beat Cooney, said "a lack of caution" in the fifth round did in Cooney.

"He may have thought Michael was tiring because Michael eased up in the fourth round," said Futch. "Cooney started coming faster and Michael was able to take advantage of this lack of caution that Cooney showed there."

Officially, the fight was even after four rounds. But Spinks was discovering in those rounds that Cooney lacked lateral movement, and that he could dodge effectively when Cooney came in.

Backpedaling and circling away from Cooney's advertised big left hook, Spinks proved an elusive target. He also found he didn't have to run as fast as he thought he would because Cooney wasn't pressing very hard. Spinks paused frequently and landed enough heavy right hands to know Cooney was vulnerable.

But a cut was opened above Spinks' right eye in the third round. Spinks said it came from an accidental butt. Cooney said he didn't remember butting. But Spinks, who wore a bandage above the eye today after having two stitches, said the blood made him step up his attack.

"I kind of cruised the fourth round," he said. "He came in a little more in the fifth. I was well-rested. I put it in my mind to put an attack on Gerry."

Spinks clipped Cooney with a left, then a hard right -- Futch had said Cooney was susceptible to a right -- when Cooney missed with a haymaker left. After that, Spinks battered Cooney into helplessness with a furious assault of lefts and rights to the head. It was surprising that Cooney managed to get to his feet twice after being driven to the canvas. "Oh, my, he's not going to go out this round," Spinks said he thought.

Spinks, deciding "I'll try something else," then shot two consecutive right uppercuts to Cooney's big jaw that prompted referee Frank Cappuccino to step between the fighters with nine seconds left in the fateful fifth. Hammering at will, Spinks landed 84 of 101 punches that round; Cooney scored only five punches. Ending it was merciful.

"I just felt I couldn't get into gear, couldn't get the mood going to become fluid," said Cooney, who met the press this morning after Spinks. "I was stiff the whole time. Waiting to catch my breath, figuring sooner or later I'd relax and be able to get more fluid.

"I was tight. I felt tight where I couldn't catch a deep breath. I don't know what it was. It was, I guess, all the things that led up to this fight.

"I never got to get going. I never got to start working the body, cut the ring off. I wasn't able to bob and weave.

"I kept my head straight up, and in the fight game that's not too good."

He had fought only seven rounds in five years before meeting Spinks, but said he did not believe the inactivity hurt him. He had gained what reputation he had fighting washed-up and obscure opponents. Aside from his defeats by Holmes and Spinks, Cooney had fought only one top 10-ranked fighter in his on-again, off-again 10-year career. At age 30, he finds himself with a 28-2 record -- his two big opportunities lost.

Today, a welt alongside his right eye but disappointment etched far more in his face, Cooney, indeed, appeared as though he had been in what was billed as a "War at the Shore." More, he looked dead in boxing's turbulent waters.

Box-Office Flop

The closed-circuit telecast of the Gerry Cooney-Michael Spinks heavyweight fight was a box office bust, the coordinator of the closed-circuit network said yesterday. Lou Falcigno, who sold the live television rights to exhibitors around the country, said less than half the closed-circuit seats for Monday night's fight were sold.

"It's very bad," he said. "It's much less than we expected."

At Capital Centre, a spokesman said 1,900 paid to see the fight.