Paris — When six-time champion Bjorn Borg decided to skip this year's French Open, many predicted an uninspiring tournament.
But 17-year-old Mats Wilander made sure his fellow Swede was not missed. With his fresh face and long blond locks, devastating two-handed backhand and formidable reserves of poise, patience,and stoicism, he resembled the youthful Borg.
In fact, though, by ground-stroking his way by Argentine veteran Guillermo Vilas 1-6, 7-6, 6-0, 6-4 Sunday in a marathon four hour and 43 minute match, Wilander bettered the legend by becoming the youngest man ever to win this prestigious tennis championship. Borg was 18 when he first succeeded here in 1974.
The women's tournament was also surprising. Six-time champion Chris Evert Lloyd did not win. Neither did such tough clay court players as Andrea Jaeger and Tracy Austin, or defending champion Hana Mandlikova.
Instead, Martina Navratilova, more comfortable on faster surfaces than the slow red clay here, displayed a new, large-size racket and a new mental toughness in sweeping to the championship over Jaeger 7-6, 6-1.
Still, the sensation of the tournament was young Wilander. In one of his first professional appearances two weeks before, he had reached the semifinals of the Italian Open. But he was not seeded here, and when he drew No. 2 seed Ivan Lendl in the third round, even he didn't expect to advance any further.
''Before the match I didn't think I could win,'' Wilander said after his baseline play and unflappable coolness had worn the usually strong Czech down in five long sets.''
Then he added, ''Don't compare me to Borg -- he's the best ever.''
No one listened, though, least of all the teen-ager. In the next round, he knocked off fifth-seeded Vitas Gerulaitus, who was playing at the top of his game.
But it was in his semifinal match against Jose-Luis Clerc of Argentina when Wilander completely won the hearts of the Parisian crowd. It was not his quickness or steadiness, but his sportsmanship that made him stand apart.
At match point, Clerc hit a forehand which the line judge called out. The umpire ignored Clerc's strenuous protests and was leaving the court when Wilander walked over and said a few words.The two players then replayed the point, and moments later Wilander had won cleanly.
''I told him (the umpire), 'I can't win like that,' '' Wilander said. '' 'He hit a winner.' ''
In the final, Wilander did not have to make any magnanimous gestures. But down one set and set point, he battled back against a rejuvenated Vilas to win.
It was a most impressive victory. Vilas had won this tournament in 1977 and, at age 30, is playing better than ever. He has added punch to his impeccable groundstrokes, and attacks more than before.
But Sunday Vilas said, ''Wilander was just stronger than me.''
Wilander did not let Vilas come to net frequently, cutting the Argentine's charges down with pinpoint passing shots. And when the match settled down into baseline rallies that lasted as long as 80 shots, the young Swede often showed more patience than his veteran opponent.
In contrast, Navratilova used her experience to spoil Jaeger's 17th birthday, which came the day before the final. Martina looked slimmer than she had in years, and more graceful on the court. She was also steadier, and her concentration, once suspect, never wandered. She credited Rene Richards, her coach, for steadying her game, and she also praised her new large-sized racket.
''You have more touch and control with it with less effort,'' she said. At the tournament, most of the players used the larger-sized rackets.''
After the final, Jaeger complained that Richards, along with basketball player Nancy Lieberman, were giving Navratilova illegal signs during the match.
''It just blew my concentration,'' Jaeger said. ''It's hard enough with one player, let alone three.''
Despite her denials and the widespread feeling that Jaeger was being a petulant loser, the accusation stained Navratilova's victory. But it should not stop her from being the Wimbledon favorite.
''At Wimbledon I'll be back on my surface, and the other girls will have to adapt to my game, not me to theirs,'' she said. ''I'm playing better this year at this time than I was last year.''
On the men's side at Wimbledon, the two Argentines who did so well here, Vilas and Clerc, will not play because of the Falklands war. Neither will Borg, who is protesting the ruling that he must play qualifying matches, or Lendl, who claims he is not properly treated at the All-England Club and who feels the grass courts there throw off his game for the Davis Cup competition which follows.
But John McEnroe, who missed this tournament because of an injured ankle, should be back in form and ready to defend the title he won there a year ago. Also prominent should be Jimmy Connors, who was top-seeded here but lost to Jose Higueros in the quarterfinals.
And of course Wilander will be there. ''I expect to be seeded this time,'' he said. ''It will be hard for me to change surfaces, though. Grass will take me some time to get used to. I have always played on clay and I am not used to grass.''