Melbourne - Martina Navratilova Sunday said Serena Williams can win 20-plus Grand Slams despite her flop at the Australian Open, adding she remains well ahead of the competition including the emerging generation of women's players.
World number one Williams was gunning to match Navratilova and Chris Evert on 18 Grand Slams, but hampered by a back problem she crashed out in the fourth round at Melbourne Park to Ana Ivanovic.
Despite the early exit, Navratilova said Williams remains "head and shoulders" above any other player on tour.
"She's 32 now -- her body failed her a little bit this week, apparently she had some issues with her back," Navratilova told the Melbourne Herald Sun.
"But if she stays healthy there's no doubt in my mind that she'll go into 20-plus numbers in the Grand Slams.
"She is still the biggest competitor out there, the strongest competitor and if she's healthy, it's really hard for the other players to compete with her."
Navratilova said that while Victoria Azarenka and Maria Sharapova could challenge her on their day, "the younger generation hasn't quite caught up".
But she added that they were starting to bridge the gap.
"When I was 32, Steffi Graf was number one. She doesn't have a Steffi Graf nipping at her heels," Navratilova said.
"Although you see the new generation is here now with Garbine Muguruza, Eugenie Bouchard, Madison Keys, Sloane Stephens... the competition is catching up to her but she's still head and shoulders above everybody else."
Of those four emerging players, Navratilova highlighted Spain's Muguruza as one to watch.
"She's just got to keep improving, keep getting the experience and work on her game," she said of the 20-year-old.
"She's got all the goods. She's got a good head on her shoulders, she wants it, she's not rushing, she's developing in her own time and she's got the body for it."
Muguruza, 20, beat former world number one Caroline Wozniacki at the Australian Open before losing to fifth seed Agnieszka Radwanska in the fourth round.
She won her first WTA title at this month's Hobart International, an achievement even more impressive in that she was a qualifier.