U.S. Open mixed doubles: Venus Williams out in first round

Venus Williams showed that her serve knows no age, but she and teammate Reilly Opelka lost their first-round match in the U.S. Open mixed doubles competition to Russia's Andrey Rublev and the Czech Republic's Karolina Muchova on Tuesday in New York.

Rublev and Muchova prevailed 4-2, 5-4 (4) despite the American duo combining for 11 aces. Facing break point with the second set tied 3-3, Williams smashed an ace past Rublev, the 15th-ranked ATP player and someone nearly 18 years Williams' junior.

The Williams-Opelka team had more winners (18-15) but also more unforced errors (14-8) in the match. After they won the seventh game of the second set, Rublev and Muchova forced the tiebreaker and went ahead 3-1. The Americans rallied to tie it 4-4 before losing the final three points.

Williams, 45, will continue her stay in New York as a wild-card entrant in the women's singles draw.

--Semifinalists determined

Meanwhile, Rublev and Muchova did not last much longer in the mixed doubles draw as the Italian team of Andrea Vavassori and Sara Errani beat them in the quarterfinals 4-1, 6-5 (4). Vavassori and Errani knocked off the second-seeded team of Taylor Fritz and Kazakhstan's Elena Rybakina 4-2, 4-2 in their opener.

Vavassori and Errani will meet American tandem Christian Harrison and Danielle Collins in the semifinal round.

Harrison and Collins opened by defeating German Alexander Zverev and Switzerland's Belinda Bencic 4-0, 5-3, while fellow Americans Ben Shelton and Taylor Townsend upset No. 4 seeds Holger Rune of Denmark and Amanda Anisimova 4-2, 5-4 (2). In the quarterfinal showdown, Harrison and Collins outlasted Shelton and Townsend 4-1, 5-4 (2)

In the other semifinal, the top-seeded duo of Brit Jack Draper and Jessica Pegula will meet the third-seeded tandem of Norway's Casper Ruud and Poland's Iga Swiatek.

Draper and Pegula took care of their big-name first-round opponents, Spaniard Carlos Alcaraz and Britain's Emma Raducanu, 4-2, 4-2. Alcaraz had a quick flight from Cincinnati after winning the ATP 1000 title there on Monday.

Then Draper and Pegula cruised past Russians Daniil Medvedev and Mirra Andreeva 4-1, 4-1 in the quarters. The Russians had prevailed 4-2, 5-3 over Serbians Novak Djokovic and Olga Danilovic in the first round.

Swiatek won the women's title in Cincinnati on Monday night and was plenty sharp on Tuesday as she and Ruud beat Frances Tiafoe and Madison Keys 4-1, 4-2. In the quarters, they beat Lorenzo Musetti of Italy and Caty McNally by an identical scoreline. McNally and Musetti had previously beaten Frenchman Gael Monfils and Japan's Naomi Osaka 5-3, 4-2.