An examination yesterday in Detroit revealed that Thomas Hearns broke several bones in his right hand in his middleweight fight with Marvelous Marvin Hagler Monday night. The injury was responsible for Hearns changing his strategy in the fight, one of his corner men said.

Prentis Byrd said yesterday that Hearns came back to his corner after the first round and said, "I think my hand's broken." Emanuel Steward, Hearns' manager, then advised, "Just box him. Take the (left) jab and work on the cut (above Hagler's right eye)," Byrd said in a telephone interview from Detroit. Hagler won the fight on a third-round knockout.

Thomas Magnell, a Detroit orthopedic doctor, examined Hearns and found metacarpal fractures of the fighter's right ring and pinky fingers.

Byrd said Hearns incurred the fractures when he hit Hagler with a right uppercut in the first round.

He maintained that if Hearns had not injured his hand, "he could have gone toe to toe with Marvin." Instead, after a first round that featured exceptionally hard punching by both fighters, Hearns had to take a more tactical and defensive approach, Byrd said.

"There are certain moves that Thomas has in which he moves side to side and then throws the right," Byrd said. "After he hurt the hand, he would throw the left instead, and it was more of a jab than a punch. Sometimes he threw the right, anyway, but it wasn't the same. I could tell that. By the end of the fight, he could hardly throw a right hand, it hurt so much."

Byrd said Hearns has had injuries in the right hand before, but they occurred near the wrist. He also indicated there was no discussion in the corner whether Hearns should stop fighting.

"We could never have told him," Byrd said. "He would have looked at me like I was nuts. He had a guy who was bleeding like a stuck hog."

Had Hearns not opened the cut over Hagler's eye, he might have had a better chance at winning by boxing despite the broken hand, Byrd said. "If (Hagler) wasn't cut, he wouldn't have come on so strong," he said.

Hearns' hand will be in a cast for about six weeks and he should be able to do light punching in two months, Byrd said. Steward said his fighter would defend his WBC super welterweight title in November against John Mugabi of Uganda.