Sean Kanan had every reason to celebrate during the Christmas holidays of 1988. Only months before, the green-belt karate student had beaten out more than 2,000 other martial arts hopefuls for the part of Mike Barnes, Ralph Macchio’s sultry, sneering nemesis in The Karate Kid Part III. After two weeks of filming in Los Angeles, the cast and crew of the John Avildsen sequel had gone on their seasonal break, and Kanan grabbed his then girlfriend and headed for Las Vegas. There, in the lobby of the Dunes Hotel, Kanan dropped a quarter in a slot machine, said, “I think I’m going to faint”—and fell to the floor.

Unconscious when hotel security guards reached his side, Kanan came to, but during the 10-minute drive to Humana Hospital-Sunrise, paramedics were unable to raise his alarmingly low blood pressure. In the emergency room, the reason for their failure became clear: Kanan had two quarts of blood pooled in his abdomen, the result of heavy internal bleeding.

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Kanan, 22, traced his injury to a period of shooting four days earlier, when, to simulate being thrown through a door, he had to lunge forward seven feet and land on his stomach—for 20 takes. The successive knocks left the actor bruised and aching. To ease the pain, he took aspirin, a blood thinner, and unwittingly quickened the abdominal hemorrhaging.

Yet as he lay on an emergency-room stretcher, Kanan was less worried about survival than job security—and completing the film. “I don’t have time for an operation,” he said. Retorted the doctor: “I don’t even know if we can save your life.”

Still on the stretcher, Sean was stunned. “I didn’t see the proverbial light at the end of the tunnel,” he remembers, “but I felt myself getting very cold and very tired like I was slipping away. I stayed awake by telling myself, ‘It’s going to be all right.’ ”

Fortunately, it was. “Everyone was saying, ‘You should be thankful you have your life,’ ” Kanan recalls. “I was. But it didn’t go very far toward easing the pain of possibly losing the movie.” The day after the hour-long surgery to repair a tear in his abdominal wall, he got up and started walking—IV stand in tow. “It was painful,” he says, “but I knew if I didn’t get out of bed, I would lose the part.” That same day Kanan was on the phone with director Avildsen, begging him not to recast his role. Avildsen, recalling how difficult it had been to cast the villain, was finally persuaded to wait. “It was another chunk of gray hair,” says the director, “but Sean was by far the best actor. It made more sense to rearrange our shooting schedule to accommodate his healing.”

Kanan had been obsessed for years with winning a place in the movie. Born Sean Perelman, the son of a New Castle, Pa., jewelry chain store owner, Dale Perelman, and Michele, a real estate agent, he started taking karate lessons at age 13. He saw the first Karate Kid when he was 17 and has since seen it and Karate Kid II 10 times each. In 1986, when he heard that another sequel was in the works, the Boston University sophomore decided to chop his way into the action. During his two years studying political science at BU, he applied his teenage modeling experiences to acting classes and landed a few bit parts in ABC’s Spenser: For Hire. He transferred to UCLA in his junior year and hired a manager who told him to change his name. “It’s strong sounding,” Kanan says of his choice. “It has a slight biblical quality.”

Like Goliath, perhaps. After answering an open casting call for The Karate Kid Part III, Kanan was called back for a screen test with Macchio. “I wanted them to remember me,” Sean says. “So I backed Macchio into a corner and wouldn’t let up. Ralph was like, ‘Call him off!’ ”

Once back on the set after his operation, Kanan insisted on doing his own karate scenes. “It was very brave of him,” says Avildsen, who had planned to use a double. “I didn’t want to see him injure himself. Ultimately, it’s only a movie.” Kanan, however, had a compelling argument: “I felt that if I didn’t do something like that again, I was always going to have that subconscious fear of injuring myself.”

Kanan’s courage paid off in a performance the Hollywood Reporter called “terrific.” Now basking in the movie’s success, he has eased up on the karate and stepped up the dating. Gone is the girlfriend who witnessed his Las Vegas swoon. These days his most frequent companion is Miss USA of 1988, Courtney Gibbs, 22, whom he met at an art show. It is not serious. “I’m trying to avoid that,” Sean says. “I want to spend time with my friends.”

Home base is a barely furnished, one-bedroom West Hollywood apartment stocked with nutritious canned okra and refried beans sent by Mom and the M&M-studded cookies he’s more likely to eat. As for future projects, Karate’s bad boy will be seen this fall in Fox TV’s remake of The Outsiders, the S.E. Hinton novel turned 1983 movie that introduced such big-name brats as Tom Cruise, Rob Lowe—and Ralph Macchio. It’s another nasty-guy role, but Kanan’s not afraid of typecasting. “A lot of people started off as bad guys,” he figures. “Humphrey Bogart did, right? I could do worse.”