U.S. Open Appears to Be Open : Tennis: Edberg and Graf are each seeded No. 1, but there will be plenty of challengers at Flushing Meadow.

NEW YORK — The 110th U.S. Open begins today at Flushing Meadow with Stefan Edberg and Steffi Graf top-seeded and favored to win the year’s fourth and final Grand Slam tennis event, which is expected to have its usual two weeks of heat and humidity.

But this U.S. Open will not be routine. For the first time in 21 years, there will be no Jimmy Connors.

The five-time U.S. Open champion played an exhibition match Saturday against Ivan Lendl at Forest Hills, but Connors retired in the third set, complaining of exhaustion and leg cramps.

Connors, who will be 38 next Sunday, has played one tournament match this year and that was in February.

” . . . if you thought I could come in here and win the Open, thank you very much, that’s some awful strong confidence and I appreciate that, but for someone 38 to go out and feel they can be out for six months and go into the U.S. Open--you’re fooling yourself, but you’re not fooling me,” Connors said.

If Connors is on the sideline, can 31-year-old John McEnroe be far from joining him?

Because of his No. 21 ranking, McEnroe is not seeded. He will play Javier Sanchez Vicario in the first round and could play 10th-seeded Andrei Chesnokov in the third round.

McEnroe, who lost to Edberg in the semifinals Saturday of the Hamlet Challenge Cup, is only 7-5 since playing at Queens.

Edberg’s analysis: “He’s a bit slow . . . not as quick as he used to be.”

Slowly but surely, McEnroe is winding down, but he is not expected to be a factor to challenge for Boris Becker’s crown anyway. Nor would have Connors.

The list of real contenders is long, according to Michael Chang: “There’s no one dominating men’s tennis any more. You got some people who win a little more than others, but there’s nobody who really stands out.”

Edberg might come the closest. Ranked No. 1 for the first time, the 24-year-old Edberg has won his last three tournaments--at Wimbledon, Los Angeles and Cincinnati--and owns a 17-match winning streak.

Edberg’s hard court record of 31-3 is the best on the IBM/ATP Tour. Becker has not won a Grand Slam title this year, which might make him more dangerous. Although he lost to Edberg in the Wimbledon final for the second time in three years (Becker beat Edberg in the 1989 Wimbledon final), he has jumped over Lendl to No. 2 and won the U.S. Hardcourt title in Indianapolis.

One player Becker will watch out for is 18-year-old Yugoslav left-hander Goran Ivanisevic, who is in his quarter of the draw. Becker lost to Ivanisevic at the French Open and won a close four-set match at Wimbledon.

Lendl, a three-time U.S. Open champion, is seeded third, his lowest seeding in eight years. Last year, Lendl equalled Bill Tilden’s record of eight U.S. Open final appearances, although he lost to Becker in four sets.

Fourth-seeded Andre Agassi and Chang, seeded 11th, could have an impact, but Agassi’s hard court results have been disappointing recently. He lost to Chang in Toronto and to Peter Lundgren in Cincinnati.

Agassi’s 20-4 hard court record is second only to Edberg’s.

Chang, who has a busy schedule the rest of the year to make up for tournaments lost because of his hip injury, won in Toronto and lost to Edberg in the Los Angeles final.

At the same time, the women’s field is equally as wide open and more clear-cut. Graf remains the favorite to win her third consecutive Open title, but she must dispel notions that her game has been affected by her father’s widely publicized personal problems.

The primary challengers to Graf are second-seeded Martina Navratilova and third-seeded Monica Seles. If form holds through to the semifinals, Seles would play Navratilova in a rematch of the Los Angeles final, which Seles won in three sets.

Fourth-seeded Zina Garrison is once again in Graf’s path and so too is 13th-seeded Jennifer Capriati.

According to eighth-seeded Mary Joe Fernandez, “It’s an open Open.” Consider:

--Graf lost to Seles in the French Open final. Navratilova did not play.

--Garrison beat Seles in the Wimbledon quarterfinals. Garrison beat Graf in the semifinal. Navratilova beat Garrison in the final.

--Navratilova beat Garrison in a semifinal at Los Angeles. Seles beat Navratilova in the final, but only by winning a third-set tiebreaker, 8-6. Graf did not play.