Williams, 37, returned from giving birth to her first child in September last year to reach the Wimbledon and US Open finals, but suffered upset losses in both to leave her stuck on 23 major wins
American number three Madison Keys said she has no doubt Serena Williams can equal the record of 24 Grand Slam titles despite her stormy defeat in the US Open final.
Keys said Williams, who argued furiously with the umpire during her shock loss to Naomi Osaka in New York, certainly had Margaret Court's all-time mark as a target.
Williams, 37, returned from giving birth to her first child in September last year to reach the Wimbledon and US Open finals, but suffered upset losses in both to leave her stuck on 23 major wins.
"I definitely think she can do it, and I definitely think it's something that she thinks about," Keys told AFP at the WTA Elite Trophy at Zhuhai in China.
"I think she wants it and I think when Serena puts her mind to something, it usually happens," she added.
Keys, 23, started playing tennis after watching Williams and her sister Venus on television and has often cited them as an inspiration.
"She came back and she played three Grand Slams and made two finals," the world number 16 said.
"No one is ever going to be Serena and I think she's done a ton for the sport and has helped players like me a lot," she added.
She said it will be a "big loss" when Williams finally retires, but that she would remain a major figure in tennis.
"Obviously when she decides to stop playing it's going to be a big loss but I think she'll always be a part of it, and she's always going to hold all these records and still be the greatest tennis player ever.
"So I think we'll always have her in the sport even through she's not playing."
Until Sloane Stephens won last year's US Open, the last American woman to lift a major trophy, apart from the Williams sisters, was Jennifer Capriati in 2002.
But Keys said American women's tennis was in "pretty good" shape. Sixth-ranked Stephens, the current American number one, was runner-up at last week's WTA Finals.
"Sloane has obviously done really well this year, I think I'm one of the US players who's had a pretty good season this year," Keys said.
"I think there's a lot of really great American players and I think the younger ones have done a really great job this year."
Asked if anybody on the current tour will ever match Williams's achievements, Keys said: "Everything's always possible.
"But to do what she did, especially as she started at such a young age, and to keep continuing to be so good, I think it would be very difficult."
Keys beat top seed Daria Kasatkina in her opening match in Zhuhai, which follows the round-robin format until Saturday's semi-finals. She will next play China's Wang Qiang.