Phil Johnson saw something in Mark Eaton right away. A ball went through the basket in the Westminster College gym, knocking the net up over the rim, and the 7-foot-4 Eaton reached up and pulled down the net. "I thought," the Jazz assistant coach says now, smiling, "there was something special about this guy."

Otherwise, not much about Eaton in those early Jazz days suggested he'd become an NBA All-Star center. After playing all of 41 minutes as a UCLA senior, here he is, seven years later, joining Akeem Olajuwon, Moses Malone and Kareem Abdul-Jabbar in Sunday's game in the Astrodome.Eaton was not voted to the West team by the conference's coaches because he's having a great statistical season. He's scoring only 6.2 points a game, is barely in the league's top 10 with 10.2 rebounds and is not even leading the league in his specialty - his 4.0 blocked shots are below his career average.

Eaton is in Houston because of what he's done for all his career - cause other people trouble. "He just changes the game," says San Antonio Coach Larry Brown. "You see things that happen when Mark goes out of the ballgame," says Jazz Coach Jerry Sloan. "It's amazing what one guy can do, without being that much involved in the offensive part."

Brown even says, "He's probably as valuable a player as there is in the league."

This is the same Larry Brown who recruited Eaton to UCLA out of junior college, but played him only 155 minutes as a junior. On the team bus after an NCAA Tournament loss to BYU, reviewing the just-ended season, Brown told an assistant coach, "I think we made a mistake."

Brown says now, wistfully, "I had never played zone . . . I had never been around a 7-foot-4 kid before." Brown was unable to correct his mistake of not playing Eaton, leaving the next season for the New Jersey Nets. The new coach, Larry Farmer, never bothered with Eaton, leaving him home from the last road trip of the season.

Coming to the Jazz as a fourth-round draft choice, though, Eaton figured he had a chance. "The guy who believed in Mark all along, more than anybody, was Mark," says Keith Glass, formerly Brown's assistant and now Eaton's attorney.

Part of Eaton's assurance was knowing he could go back to being an auto mechanic. "I went into basketball with the idea that if it didn't work out, I could do something else," he says. "There was confidence in my defensive ability, in blocking shots; a couple of things that I thought could carry me a little ways."

Sure, he could be a backup center for a few years and make a decent living.

Now look at him. He's the heart of the best defensive team in the NBA in the last 15 years and stands to cash in big-time when he becomes an unrestricted free agent after the 1989-90 season. After all, his friend and former Jazz teammate, Danny Schayes, last summer commanded $8.7 million over six years. Eaton makes $670,000.

"I'm kind of looking forward to next year," said Glass. "The numbers are staggering . . . I know this marketplace."

Jazz general manager David Checketts would have dealt with Eaton last summer, except he had to worry about Thurl Bailey, John Stockton and - unexpectedly - Karl Malone. He plans to contact Glass after this season regarding Eaton, who's 32 and figures he has at least four or five good years left in the league. "I'm sure it's going to be tough," says Checketts, remembering the summer-long battle in 1985.

"We're just going to sit back," says Glass. "Whatever anybody wants to do with us is fine. Guys certainly less valuable than Mark are going in, and continue to go back to the Jazz to redo their contracts two or three times, and we're just sitting back."

If Eaton's market value is going up, so is his acceptance in the Salt Palace. Frequently booed last season when he struggled with his hook shot, the crowd has cheered him regularly since the '88 playoffs. "You've got to give Mark some credit for hanging in there," says Malone.

"All-Star or not, if I have a couple of bad games in a row, the boo-birds will be back," Eaton says.

Curiously, Eaton's rise in popularity comes when he's hardly a part of the Jazz offense; he stays on the other side of the floor and most of his points come from offensive rebounds. "I think I'm involved in the offense," contends Eaton. "I enjoy setting screens and getting guys open."

That makes Mark Eaton the player he is, being satisfied with doing what he does best and making himself uniquely valuable to the Jazz. With 6-foot-11 center Bill Laimbeer, Detroit's field-goal defensive percentage is better than the '87-88 Jazz's - which was the best of the '80s in the NBA. The Jazz's figure (.434) is even better this season, though, mostly because of Eaton.

"There are some pretty good teams that have adjusted to not having a dominant center inside," says Checketts, always the negotiator. He also admits, "It's difficult to think what our team would be like without him."