Calling it "the saddest day of my life," Guillermo Vilas said he will retire from professional tennis.

Vilas, 32, made the announcement after losing in the Grand Prix of Bologna tournament to little-known Yugoslavian player Goran Prpic, 6-3, 6-4.

"I don't know who to blame if it's not myself," Vilas told reporters after the defeat. "I apologize to the (tournament) organizers, the city of Bologna and to all the public. In this moment, I do not feel the courage to go on the court and I feel certain that the match with Prpic was the last game of my life."

Vilas said last month he would retire if he could not improve his ranking within a year. In 1977, he was the singles champion at the French Open and the U.S. Open, and scored 13 other singles victories en route to a record 50-match winning streak . . .

In Marbella, Spain, Martina Navratilova said she plans to retire from tennis within two years.

Navratilova, 28, is spending several days relaxing in the coast resort. She told the Spanish news agency EFE that after retiring from professional tennis she plans to devote herself to her "big hobbies": reading, viewing films and participating in a foundation named for her and dedicated to underprivileged youngsters.