Serena Williams' bid to break the women's all-time Grand Slam singles title record could be beyond her, according to former British number one Sue Barker.
Williams, one short of Margaret Court's record of 24, lost in straight sets to Canada's Bianca Andreescu in the US Open final on Saturday night.
"Serena will be looking at it, 44 per cent of first serves in, that's not good enough," Barker told BBC's Sportsweek.
"She said afterwards she doesn't know what happens and the real Serena doesn't show up in the finals and that's what she's got to find the answer to.
"But maybe the pressure of the record is just too much."
Williams has now lost in her last four Grand Slam finals and television presenter Barker, who won the French Open in 1976, feels the American could be running out of time.
Barker said: "There are players out there who aren't afraid of her anymore – that's the difference.
"She had this aura about her before, she was so dominant in the finals, nobody could get near her, she played the big points so well.
"But (on Saturday night) it was the youngster who played the big points better."
Williams, who gave birth to her daughter, Alexis, in September 2017, won her last Grand Slam singles title at the Australian Open in 2017.
She has since lost in finals to Angelique Kerber (Wimbledon 2018), Naomi Osaka (US Open 2018), Simona Halep (Wimbledon 2019) and Andreescu (US Open 2019).
"She turns 38 later this month," Barker added. "She is an incredible athlete and she's been in four Grand Slam finals since she gave birth to her daughter.
"So she's still right up there, she's still doing well. If she's still motivated and wanting to do it, I think she will carry on.
"Let's face it, she's got another four (Grand Slams) next year and the Olympics, I'm sure she'll want to do that, she loves playing at the Olympics.
"That will be the motivation. But there are so many good players."
