Ivan Lendl, once the most physically fit man in tennis, announced his retirement from the game yesterday because of a back condition.

"This is a very difficult and sad time for me," 34-year-old Lendl, who is currently ranked No. 54 on the ATP Tour, said yesterday on a teleconference call. "This is not the way I would have chosen to retire and I'm sure I will miss the game I love."

Doctors diagnosed Lendl's problem as facet joint syndrome, a degenerative spinal condition, in February and he has been receiving treatments all year. Last week, however, doctors told him that there was no hope of recovery and that the pain would only worsen if he continued to play tennis. After spending the weekend wrestling with the decision, Lendl, the leading money winner in the history of men's professional tennis, decided Monday to call it quits.

"I have been trying to get better and play a few senior events, but I realized I can't even play in those because of the pain and the back spasms," said Lendl, who retired from his last match in the second round of the U.S. Open, a tournament he won three times. "It's impossible to say when I'll accept {retirement} mentally, but I have been dealing with it since the U.S. Open, and maybe I am on the way."

In his 17-year career, Lendl compiled 94 singles titles, including eight Grand Slams, and held the men's No. 1 ranking for 157 consecutive weeks and a record 270 weeks total. He was in the top 10 for 13 consecutive years and won at least one tournament every year from 1979 through 1993. And, while his prize winnings of more than $20.5 million make him the all-time leader, a German magazine that once added his prize money, appearance fees, exhibitions and endorsements reported Lendl has made $140 million from the sport.

He never won tennis's most elusive prize, Wimbledon, and his 1994 season was full of disappointment. But, he told reporters yesterday, he knew he represented an era of tennis and believed he could continue to make an impact on the game. Until this weekend.

"That closes out the big five of the '80s -- now they're all gone," tennis commentator Bud Collins said, citing Chris Evert, Martina Navratilova, Jimmy Connors and John McEnroe. "{Lendl} was a truly great player, but he had more than an iron will, he had a kryptonite will, and that caused him problems sometimes with other players and with the media."

In fact, for most of his professional career, Lendl and his booming forehand have been dogged by an image as cold and mechanical. While that has softened some since he became a U.S. citizen in 1992, most fans still see him as the serious, detail-obsessed player he was on the court. But Lendl, who sits on the board of directors of the Hartford Whalers, likes to listen to Howard Stern and breeds German shepherd dogs, said the labels are unfair.

Those who know him well agree. Tomas Smid, who played on the Czechoslovakian Davis Cup team with Lendl for seven years and remains a close friend, noted that reporters and other players didn't always get Lendl's deadpan style of humor.

"He has a different sense of humor than everybody else but that doesn't make him the icy guy you saw on the court," said Smid, now the head of Italy's player development program. "He was a great champion and this is just sad because he has been losing to a lot of people he normally wouldn't lose to."

Banned by physicians from any high-impact sports, Lendl said he will now channel his competitive instincts into swimming and his beloved golf. While Michael Jordan's exploits have discouraged him from a run at the PGA Tour, he said he would like to try to lower his 18 handicap and compete at the club level. He will also devote more time to Spectrum Sports, his sports marketing firm, and his wife and four daughters.

"Ideally you would choose to win a big tournament and then retire, but that is not realistic," said Lendl, who for now has said he will not go into coaching. "I really enjoyed playing the game, I had a lot of great times and I am going to miss it."

CAPTION: Pain forced Ivan Lendl out of his final match, at the U.S. Open in September. "Ideally you would choose to win a big tournament and then retire," he said.