A pair of 21-year-old U.S. players each played their first WTA Tour quarterfinal on Friday, and Katie Volynets emerged with a 7-5, 6-3 victory over Peyton Stearns in the ATX Open at Austin, Texas.

Both players won less than half of their service points (49 percent for Volynets, 42 percent for Stearns), but Volynets converted eight of her 16 break-point opportunities while Stearns was just 5-for-14.

Next up for Volynets is a semifinal against Russia’s Varvara Gracheva, who eliminated fifth-seeded Sloane Stephens of the United States 7-6 (4), 6-3.

The other semifinal will feature fourth-seeded Danielle Collins of the United States, a 3-6, 6-2, 6-1 winner over Russia’s Anna Kalinskaya, and eighth-seeded Marta Kostyuk of Ukraine, who knocked out Germany’s Anna-Lena Friedsam 7-6 (6), 6-2.

Abierto GNP Seguros

Third-seeded Donna Vekic of Croatia pulled out a 6-2, 5-7, 7-6 (5) victory over Belgium’s Ysaline Bonaventure in the quarterfinals at Monterrey, Mexico.

Bonaventure was in constant trouble on her serve, but she saved 12 of the 15 break points she faced to stay competitive. Vekic failed to convert two match points with Bonaventure serving at 5-6 in the third set, then needed three more match points in the tiebreaker to seal the win.

Vekic’s semifinal foe will be fifth-seeded Lin Zhu of China, who defeated the United States’ Caroline Dolehide 6-3, 6-2.

Top-seeded Caroline Garcia of France cruised into the semis with a 6-0, 6-4 rout of seventh-seeded Egyptian Mayar Sherif. Garcia next will oppose fourth-seeded Elise Mertens of Belgium, who blitzed eighth-seeded Elisabetta Cocciaretto of Italy 6-2, 6-2.

–Field Level Media