TENNIS : Agassi the Adult Serves Up Much That Is Admirable : After 13 years, he has learned to show his best on and off the court.

There’s much more to like about Andre Agassi these days than a sleeker body and a bigger serve. The most fascinating quality of the new and improved Agassi is located directly above his eyebrows, an area once perceived to be full of air.

Agassi has not only become a great tennis player, but an adult as well. Those two things don’t always go hand in hand. Nor was eventual adulthood always a certainty for the young man from Las Vegas, who, not too many years ago, was viewed by the public and the press as a rock star with a tennis racket.

This one-time teeny has lost his bopper.

If he is an idol, it is to baby boomers and their sons and daughters on Wall Street. He is 29. Ancient, dude. The generation of nose rings and skateboards and baggy pants hanging off the hips doesn’t adore Andre, doesn’t even know him.

He has been with us since 1986, when he played in his first U.S. Open. That’s 13 years’ worth of long hair and bandannas and snits on the front pages of tabloids, plus snubs of Wimbledon and subsequent love affairs with the place; 13 years’ worth of incredibly good tennis and incredibly lousy tennis, of No. 1 rankings and, just a couple of years ago, a No. 144 ranking that necessitated matches in Challenger tournaments at which attendance for the entire history of the event wouldn’t match the crowd he played to in the U.S. Open here Thursday.

There have been injuries, false starts and false promises, followed by comebacks, pinnacles reached and hope springing eternal. There has been a marriage to a Hollywood star, Brooke Shields, and a divorce of a Hollywood star, Brooke Shields. There have been goals set and missed, goals set and reached; a chubby Andre and a rippled Andre, a hairy one and a bald one. He has had more ebbs and flows than the tide at Zuma Beach.

This year, and this U.S. Open, so far, has been all flow for Agassi.

In his second-round match Thursday, the now No. 2 player in the world faced German qualifier Axel Pretsch, and sent him back to his fatherland in 1 hour 34 minutes. Agassi was efficient, workmanlike. Watching the 6-3, 6-2, 6-1 victory was like going to dinner at one of those Japanese restaurants where the chef chops up your food right in front of you. Poor Axel was sushi.

On the USA telecast, John McEnroe called the match “an extended workout” for Agassi.

The first question in the post-match news conference was about McEnroe’s statement. In the old days, that would have been a fastball down the middle. Agassi would have quipped back at McEnroe, or used the opening to bury or dismiss his opponent verbally, matching what he had done on the court. The next day’s Post and Daily News, tabloids here, would have been delighted to scream: MAC ATTACKED. Or: ANDRE ANGRY.

Not any more. Agassi responded, as follows:

“I guess in hindsight you can look back and say, ‘OK, well, it’s good and it didn’t take a whole lot out of me.’ But you know, there’s always a level of intensity that goes along with a match, especially at the U.S. Open, that always makes it feel more difficult.”

Somebody else tried, making a wisecrack--and hoping for Agassi’s similar response--about the fact that he’d had so many bad line calls in one of the games that he had to win it three times, and that he ought to get extra tour points for that.

Agassi responded gently, “Was I right about those calls?”

He was asking a sportswriter for an opinion! Near the back of the room, the guys from the Post and Daily News got up and left in tears.

The essence of just about everything else Agassi had to say was along the same lines.

He responded to a question about whether he feared a likely opponent, Marcelo Rios, by saying, “He’s a really talented player, but there are a lot of guys out there to be feared.”

He responded to a question about now being the overwhelming favorite to win here by saying, “All it takes is one bad match for U.S. Open dreams to be squashed.”

He even did a little Chamber of Commerce work for his hometown, answering a question about why he has stayed there when most other tennis players move around constantly, by saying, “Anywhere you are brought up, you have an affinity for. I feel Vegas is misperceived, in many ways. It’s a beautiful area, surrounded by mountains. It’s nice to have your family and friends there.”

And so it went, Agassi being sensitive to others’ feelings, gently weighing all sides of issues before speaking, keeping things in perspective, being diplomatic. It was like a chat with Henry Kissinger.

It also felt good, was nice to see. We went to an Andre Agassi news conference and an adult broke out. For that matter, has been breaking out for some time now.

When he won the French Open in May, joining legends Don Budge, Fred Perry, Roy Emerson and Rod Laver as the only men to have won each of the four Grand Slam events, Laver was on hand in Paris. During the awards ceremony, Agassi paid proper tribute to a man who deserves all the tribute anyone can pay. The younger, hipper, more egocentric Agassi would have missed that completely.

When top-ranked Pete Sampras hurt his back and had to default from the tournament, the first player to call with condolences was Agassi. And when he has been asked for his reaction to the departure of Sampras and last year’s champion Patrick Rafter because of injuries, he has talked immediately about how such a loss hurts the tournament and the sport. The younger, hipper, more egocentric Agassi would have told us all that meant was he had a better chance to win.

In Sept. 25 in Las Vegas, Agassi will hold his annual event for his foundation, a huge dinner that will raise more millions for the cause of disadvantaged youth in his city. The younger, hipper, more egocentric Agassi would not have cared as deeply, nor worked as hard for this, as he does now.

A week from Sunday, logic says Agassi will be on one side of the net for the men’s final. If that happens, something really radical could occur. All the grown-ups in the stands, in tribute to Agassi’s newfound adulthood, might stand up as one and turn the bills of their caps forward.