Coco Gauff defeats Maria Sakkari, then wins with Christian Harrison to send U.S. into United Cup semifinals

PERTH, Australia (AP) — After a singles loss and social media drama earlier in the week, Coco Gauff did all her talking on court Wednesday in the United Cup quarterfinals.

Gauff won twice—once in singles and then a clinching victory in mixed doubles—to send the Americans into the semifinals in Sydney on Saturday.

Gauff beat Maria Sakkari 6-3, 6-2 to give the defending champion United States a 1-0 lead over Greece. Taylor Fritz, affected by knee tendinitis, had a chance in his singles match to clinch the quarterfinal against Stefanos Tsitsipas, but lost 6-4 7-5. That sent the quarterfinal match to a mixed doubles decider.

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In that match, Gauff and Christian Harrison beat Tsitsipas and Sakkari 4-6, 6-4, 10-8. It was on track for a runaway in the third-set, 10-point tiebreaker when the Americans led 4-0 and 5-1, but the Greek pair rallied to level it at 6-6. Gauff and Harrison held on for the win.

"I think I was striking the ball well today, and when that happens, my movement on the court is also good," Gauff said after her singles win. "I usually know it's going to be a good day."

On Monday, Gauff dropped a post on social media about a half-hour before she started her singles match, hoping to add context to her recent comments about American tennis fans.

The ensuing match didn't go well for the No. 4-ranked Gauff, who lost the first five games and struggled in a 6-1, 6-7 (3), 6-0 loss to No. 42 Jessica Bouzas Maneiro. But Fritz won his singles match against Spain and Gauff and Harrison combined in mixed doubles to clinch top spot in Group A.

In a night quarterfinal at Perth on Wednesday, Stan Wawrinka, playing in his farewell tour this year before retiring, was scheduled to lead Switzerland against Argentina.

At Sydney, Hubert Hurkacz and Iga Świątek were victorious in their singles matches to give Poland a winning 2-0 lead over Netherlands and a place in the quarterfinals from Group F. Poland is expected to play Australia in the quarterfinals.