Thomas Hearns learned a law of pugilistic physics today, the one that says it takes a bigger punch to lay out a bigger man.

Hearns, who once held the welterweight championship and who holds the World Boxing Council junior middleweight title, won his 10-round middleweight bout against Murray Sutherland on all cards, but not without a disconcerting moment or two.

In the first round, Hearns hit Sutherland hard and flush on the cheek with an overhand right, a punch that might have dropped some of the finest welterweights. Hearns kept up the attack, but Sutherland, a durable 160-pound Scot, kept his feet.

Hearns won the fight easily as he began to rely more on his strong left jab, left hooks and his quick feet. The blood around his eyes, though, may be a signal to Hearns that he has moved to more treacherous realms.

Hearns' last fight was in December, when he scored a decision over Wilfred Benitez in New Orleans. Since then he has injured his right hand a number of times, but today he said, "I didn't have any trouble with my right hand because I didn't get it in too often."

Hearns' trainer and manager, Emmanuel Steward, said his fighter will probably defend his junior middleweight title, fight one more quality middleweight and then challenge Marvin Hagler for the middleweight title. Hagler is scheduled to fight Roberto Duran in November, but Steward said, "I'm presuming that Hagler will win."

Hearns has lost only once. Against Sugar Ray Leonard in a welterweight championship unification fight, Hearns led on all cards until he lost on a technical knockout in the 14th round. But with Leonard retired and Hearns' frame growing stronger and fuller, the move to the middleweight division was inevitable. A fight with Hagler would bring a tremendous purse.

Sutherland, an experienced boxer who lost hard-fought light heavyweight title bouts to Matthew Saad Muhammad and Michael Spinks, said Hearns was strong enough to fight Hagler and could win because of his boxing ability. "I wanted to bully him," Sutherland said. "But he moved too good. Every time I moved in close, he was gone."

Under a circus tent near the ocean boardwalk, Hearns tried to keep Sutherland off balance. In the second and third rounds, he kept salting Sutherland with jabs, but held his right in abeyance.

In the fifth, both men picked up the pace once more. Sutherland missed with a wild right, but later in the round connected with a solid right that opened a small cut on Hearns' right brow.

Hearns then turned to the body. Sutherland, though, opened another small cut, again with a right, on Hearns' left cheekbone.

Steward said the cuts were inconsequential and said Hearns would be healed and ready to work in three weeks.

"The 10th was a go-for-bust round," Sutherland said. "I went hell-bent, caution to the wind. But I couldn't catch him."

Judge Paul Cavaliere gave all 10 rounds to Hearns, while Frank Brunette had it 7-2-1 and Richard Murray scored it 9-1.