It's 'Mac the Nice' now as former tennis bad boy wins 4th US title

The US Open Tennis Championships had just ended, but the new and improved John McEnroe still managed to come up with another sparkling return of serve. This one brought hearty laughs in a crowded press interview room just after ''Junior'' had overwhelmed Ivan Lendl in the men's final 6-3, 6-4, 6-1.

When veteran New York writer Maury Allen asked for an explanation of the rout , McEnroe put the ball in Allen's court. ''No, you explain to me how you could give that guy a hit the other night,'' he said.

The remark was in reference to the call Allen had made at nearby Shea Stadium , where two nights earlier he had been the official scorekeeper at a New York Mets baseball game. A different decision on one batted ball would have given rookie Dwight Gooden a no-hitter, and now native New Yorker and Mets fan McEnroe was jokingly taking the journalistic offensive.

McEnroe is known for his dour court countenance and angry interrogations of linesmen, but he is gradually changing his ill-tempered image, and he seized this moment to display a lighter side of himself.

Mac still can be tempestuous, but as he has now shown in the last two big tournaments, maintaining an even keel helps in steering a winning course. John kept his cool in London and walked away with one of the most lopsided victories in Wimbledon history, a 6-1, 6-1, 6-2 annihilation of Jimmy Connors. Then here, at the National Tennis Center in Flushing Meadow, he emerged again as a composed and brilliant champion.

The victory over the second-seeded Lendl was a stroll in the park, Corona Park to be precise. McEnroe held his serve throughout the match, broke Lendl's four times, and gave up fewer games than any male champion in the last decade. The championship was McEnroe's fourth in the Open, but his first since a three-year reign that ran from 1979 to 1981. The last couple years he hadn't even reached the finals, losing to Lendl in the 1982 semifinals, then dropping a fourth-round match to Bill Scanlon last year.

For a while, in fact, Lendl really had McEnroe's number, beating him seven straight times. The pendulum swung the other way, though, beginning with McEnroe's four-set victory in the US Pro Indoor at Philadelphia in 1983.

Partly on the advice of all-time great Don Budge, McEnroe went to to an all-out attacking game, forcing a strength-vs.-strength confrontation pitting his own deadly volleys against Lendl's blazing groundstrokes. Using a unique rocking-chair windup that keeps his aim well disguised, then coming to the net behind the best serve in tennis, John has managed to win 9 of their last 11 matches.

''My only realistic chance to beat him is to return his serves better,'' said the canceled Czech, who was seeking to become the first right-hander since John Newcombe in 1973 to win the United States men's title. ''I can't beat him if I don't break his serve.

''Maybe I should go out and spend lots of time practicing against left-handed servers. But it probably wouldn't do much good, because no one serves and volleys as well as McEnroe.''

Attacking is only one part of the 25-year-old southpaw's well-rounded game, however. He is also a formidable shot-returner, hitting balls on the rise with a Johnny-jump-up swing, and possessing an uncanny touch that enables him to change speeds constantly. In the final, some of Lendl's bullets came back so softly you wondered if McEnroe was playing with a seat cushion.

Lendl would have liked to lob over McEnroe, but said his opponent's flat volleys are too hard to get under. And coming in on John's second serves was no easy task either. ''He's hitting them deeper than he used to, and they're skidding, instead of sitting up,'' said a discouraged Lendl, the runner-up for a third straight year.

''I think I've gotten better this year,'' McEnroe observed, ''and I believe I can get better yet. Hopefully I'll find the motivation in some shape or form. Connors has a fire inside, and that's what I want to have.''

Interestingly, a loss to Lendl at the French Open has been something of a key to McEnroe's lofty 1984 performance (he is 66-2 on the year). The defeat, he says, caused him to bear down for the ''big ones,'' Wimbledon and the US Open, and taught him to ''save energy and keep away from controversy.''

He has tried to be less argumentative since then, and generally wears a much more peaceful expression while playing than he once did. ''This is a happy medium for me. That's what life is all about, compromising,'' he remarks philosophically. ''I never thought I'd hear him say that,'' whispers one pleasantly flabbergasted writer.

The only time in Sunday's match that McEnroe seriously questioned a call he did so with amusingly contrived horror. He dropped to the court, lay flat on his back, and held his hands up about a foot apart, the distance he felt Lendl's winner had been out.

Ultimately, John's biggest worry was that he would run out of gas. On Saturday he had ended the best day of tennis he had ever seen at Flushing Meadow by beating Connors in a five-set semifinal (6-4, 4-6, 7-5, 4-6, 6-3). The match ended after 11 p.m. and followed a three-set women's final (won by Martina Navratilova over Chris Evert Lloyd) and another men's semifinal, an epic struggle in which Lendl defeated Pat Cash 3-6, 6-3, 6-4, 6-7, 7-6.

''I don't know if the crowd really wanted to see another five-setter today,'' McEnroe said Sunday after collecting the winner's trophy and his $160,000 paycheck.

Whether the fans wanted more tennis or not, though, was all academic. The game's best player was on a roll, making swift, sure work of a rival whose world ranking could have been 102 as easily as No. 2 for all it mattered.