LAS VEGAS, OCT. 28 -- Thomas Hearns will try to become the first boxer to win titles in four weight classes when he fights Juan Domingo Roldan here Thursday night. At stake will be the WBC middleweight championship, vacated when Sugar Ray Leonard retired after upsetting Marvelous Marvin Hagler on April 6.

Leonard and Hagler, who knocked out Hearns in 1981 and 1985, respectively, will be on hand, Hagler as a commentator on the closed-circuit and pay-per-view telecast of the bout outside the Las Vegas Hilton.

"I'm evaluating the situation," said Hagler, who is a possible opponent for the winner. "I want to sit back, watch these guys and see what happens."

Hearns' attempt is scheduled for 11 p.m. EST, after Bobby Czyz's scheduled 15-round IBF light heavyweight title defense against Charles Williams.

Tonight at the Hilton, Milton McCrory got up from a fourth-round knockdown, scored one himself in the sixth and retained the North American Boxing Federation super welterweight (154-pound) title with a one-sided 12-round decision over Herman Cavesuela.

In an upset in a fight for the vacant NABF lightweight (135) title, Primo Ramos knocked out Frankie Randall, the WBC's No. 1 contender, in the second round.