"Some people may be tested once a month and then some get tested maybe once or twice a year," she said. Anti-doping authorities "need to figure that out a little bit better, but overall I think tennis is in pretty good hands."
Navratilova is teaming with that other famous Martina, five-time major winner Martina Hingis, in the legends doubles event. The Martinas beat Lindsay Davenport and Cara Black in a single set 7-6 (4) on Monday.
THE NEXT SERENA: Three-time major winner Lindsay Davenport doesn't believe the future of American women's tennis will be so bleak once Serena Williams retires.
Davenport, in Melbourne to play in the Australian Open legends event, says teenagers Sloane Stephens and Madison Keys have the kinds of weapons necessary to become future top-10 stars.
"It's not about just getting the ball back in play anymore. It's about being able to finish points. It's about having a good serve. I think both of them have that," she said.
Stephens, 19, will play Williams in her first Grand Slam quarterfinal Wednesday. Keys, 17, upset Austria's Tamira Paszek in the first round at Melbourne Park before losing to fifth-seeded German Angelique Kerber in the third round.
Davenport predicts it will be a few years, however, before Williams is ready to quit. She foresees Williams winning a few more major titles.
"She's at 15. The next record for her to break would be Martina (Navratilova) and Chris (Evert) — they're at 18. I think she'll for sure get to 19," Davenport says.
TWEETING WITH THE ENEMY: It was 4 a.m. on Monday, about two hours after Novak Djokovic had ripped off his shirt to celebrate his thrilling five-set win over Stanislas Wawrinka in the Australian Open.
But before turning in, Djokovic fired off one last tweet. It was to his opponent.
"Stan, thank you very much!! I am sorry for your loss.. Wish you all the best for the rest of the season.. It was great pleasure," Djokovic wrote.
Still awake himself, Wawrinka replied four minutes later: "Congrats for the fight tonight! Good luck for the rest of the tournament."
Then the 27-year-old Swiss player tweeted another message in French: "Ça fait mal... Très mal ........" or "That hurts. Really hurts."
Djokovic next faces No. 5 Tomas Berdych in the quarterfinals.
Associated Press Writer Jocelyn Gecker contributed to this report.