NEW HAVEN, CT, USA -- British No.2 Heather Watson earned a hard-fought victory on Thursday at the Oracle Challenger Series New Haven, edging Spain's Sara Sorribes Tormo, 6-3, 4-6, 6-4 to advance to the quarterfinals of the WTA 125K Series event.

World No.101 Watson, seeded No.11 this week, is contesting her first event since a first-round defeat to surprise package Mariam Bolkvadze in the opening round of US Open qualifying two weeks ago. Watson needed to utilize all of her grit to eke out the win over No.6 seed Sorribes Tormo, before emerging victorious after two hours and 21 minutes of play.

Sorribes Tormo had 15 break points in the match, but was only able to convert five, while Watson was far more successful when she had opportunities to steal her opponent's service games, going 7-for-9 on break points.

Watson jumped out to a big lead in the first set, crushing a superb backhand passing shot for a winner to break Sorribes Tormo for a second time and reach 4-1. Serving for the set at 5-2, Watson handed back one break after a series of unforced errors, but broke the Spaniard for a third time to close out the one-set lead.

Despite falling behind an early break, Sorribes Tormo fought back in the second set, as her own passing shots improved while Watson's unforced error count crept ever higher. After the players jockeyed back and forth en route to 4-4, Sorribes Tormo earned a critical break in that game after blasting a winner down the line on break point. The Spaniard coolly served out the set at love to level the tilt at one set apiece.

Watson found the range on her forehand to notch a 4-1 lead in the decider, before Sorribes Tormo roared back to 4-4. Watson earned a pivotal service hold in that game, which was filled with long all-court rallies, fending off two break points in the process. Now up 5-4, Watson reached double match point on the Spaniard's serve, and completed the break and the match with a deft dropshot that landed on the sideline for a winner.

Watson will now face American Danielle Lao in the quarterfinals, after Lao got past Paraguay's Veronica Cepede Royg, 7-6(3), 0-6, 6-1. Cepede Royg was unable to win two singles matches in a day, as she had completed her interrupted second-round victory over No.16 seed Francesca Di Lorenzo earlier on Thursday.

No.2 seed Jennifer Brady, the highest seed remaining in the draw, defeated her fellow American Nicole Gibbs, 6-4, 6-3. Brady sets up a quarterfinal meeting with No.7 seed Anna Blinkova of Russia, who eliminated No.12 seed Christina McHale of the United States, 7-6(1), 6-2. Blinkova pushed World No.1 Naomi Osaka to three sets in the first round of the US Open last week.

Another American, No.3 seed Lauren Davis, got past her compatriot, No.15 seed Varvara Lepchenko, 4-6, 6-0, 6-4. It was Davis's second straight three-set tussle with another American after her second-round victory over Sophie Chang on Wednesday. In the quarterfinals, Davis will meet No.5 seed Pauline Parmentier of France, who outlasted American Ann Li, 6-4, 4-6, 7-5.

Every quarterfinal match will feature one American, as Usue Maitane Arconada of the United States moved into the elite eight after her opponent, Slovakia's Jana Cepelova, retired from their clash while trailing 6-0, 4-1. Arconada will meet No.9 seed Astra Sharma of Australia, who beat Russia's Varvara Flink, 7-5, 6-1.