Former British number one Johanna Konta was "watching in awe" as successor Emma Raducanu claimed the US Open title.
Raducanu, 18, has risen to 22nd in the world rankings after becoming the first qualifier to win a Grand Slam.
She is now in California, where she will compete as the 17th seed in the BNP Paribas Open.
"Because it's never been done before, it's going to be one of those captivating moments in sporting history," Konta said of Raducanu's win.
The 30-year-old told BBC Radio 5 Live: "I was watching in awe. She really took it in her stride.