Serena Williams has suffered her second defeat on her farewell tour.

The 40-year-old, who announced her retirement the previous week, lost 4-6, 0-6 to 19-year-old US Open winner Emma Raducanu of Great Britain at the Cincinnati Masters in Mason, Ohio, on Tuesday evening (local time). The hard court tournament, officially the Western & Southern Open, was the 23-time Grand Slam winner Williams’ last stop before the US Open in New York, which begins on 29 August. Raducanu committed only one unforced error in the match, compared to Williams’ 19.

“I can’t believe I just played against Serena Williams. I think I’m really lucky that I was able to do that and that our careers crossed even though the age difference is so big,” Raducanu said. “I just knew how important every single point was, because if you let up just a little bit, she will roll over you. She’s just a legend.” Williams did not speak to the media after the match.

The former world number one had lost 2-6, 4-6 in the second round at the WTA tournament in Toronto a week ago to Olympic champion Belinda Bencic of Switzerland. A day earlier, Williams had announced that she would soon end her career. The US American is expected to retire after the US Open.