(CNN) — Serena Williams’ illustrious doubles career has likely come to an end after she and her sister Venus fell in straight sets to the Czech duo of Linda Nosková and Lucie Hradecká in the first round of the US Open at Arthur Ashe Stadium in New York.

The 23-time grand slam singles and 14-time doubles champion is still set to play against Australia’s Ajla Tomljanović in the third round of the singles draw on Friday. Venus Williams lost in the first round on Tuesday.

Thursday night might have been the last match for Serena and Venus as a doubles team. The Czech Republic duo of Nosková, 17, and Hradecká, 37, advanced to the second round, winning 7-6(5), 6-4.

“I think we did a very good job, and I’m so sorry for you that we beat them, but we are so happy we did it,” Hradecká said to the 23,000-plus fans in an on-court interview moments after the match.

It was the first time she had teamed with Nosková in doubles.

The Williams duo started well and had two set points with a 5-4 lead in the first, but the Czechs fought back. Hradecká and Nosková also trailed in the tiebreaker but won the last four points.

They appeared to have a commanding 4-1 lead in the second set, but Venus and Serena were able to win three consecutive games to tie it up. But the Czechs held serve to go up 5-4 then broke Serena in the final game with Hradecká hitting a backhand at the net in between the sisters for the match winner.

The Williams sisters entered the US Open as a doubles’ wild card. They last played doubles together in the 2018 French Open, when they reached the round of 16.

On Wednesday, Serena defeated Anett Kontaveit 7-6(4), 2-6, 6-2 in singles play. It was Williams’ fourth match since announcing in Vogue magazine she will “evolve away from tennis” after the US Open.

“I have never liked the word retirement. It doesn’t feel like a modern word to me. I’ve been thinking of this as a transition, but I want to be sensitive about how I use that word, which means something very specific and important to a community of people,” Williams, 40, said in the Vogue article published earlier this month.

“Maybe the best word to describe what I’m up to is evolution. I’m here to tell you that I’m evolving away from tennis, toward other things that are important to me,” she said.

Venus Williams, 42, has not announced her future tennis plans.

If they do both leave the sport this year, they will do so having amassed 48 Grand Slam titles (singles, doubles and mixed doubles) as a family and holding a perfect mark in doubles finals (14-0). They also won three Olympic gold medals in doubles and each won a singles’ gold.

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