Martina Navratilova celebrated her 31st birthday by beating Chris Evert, 7-5, 6-1, in the final of the $175,000 Virginia Slims tennis tournament yesterday in Filderstadt, West Germany.

She needed only 73 minutes to win her choice of $36,000 or a sports car. She took the car.

"I took one last year, and I'll take this one, too," she said. She's won the tournament four times.

Evert earned $16,000. Steffi Graf, top-ranked in the world, didn't compete. It was Navratilova's third tournament victory this year and made her 40-35 against Evert.

After a 21-minute game, Evert led the first set, 4-2. After her lead fell to 5-4, she never again held serve . . .

Ivan Lendl won $55,000 by beating Wimbledon champion Pat Cash, 6-4, 6-2, 6-4, in the final of the Australian Indoor Championship. Cash said his semifinal victory over second-seeded Boris Becker had tired him out. He had been 2-0 against Lendl this year. . .

Tim Mayotte broke serve in the first game of the last set and beat Ricki Osterthun, 6-2, 5-7, 6-4, to win a $240,000 Grand Prix event in Toulouse, France. . .

The men's team from Annapolis beat the team from Jonesboro, Ark., 5-0, to win the national championship recreational USTA League title in Seabrook Island, S.C., at the 4.0 level.