American Danielle Collins grabbed her second WTA tour title just two weeks after claiming her first with a hard-fought victory over Daria Kasatkina in San Jose, California, on Sunday.

Collins, the 27-year-old who became the tour's 14th first-time champion of 2021 with her claycourt title in Palermo last month, kept the momentum going on the hardcourts of California with a 6-3, 6-7 (10/12), 6-1 victory.

It took longer than it might have, seventh-seeded Collins serving for the match at 5-3 in the second set but letting five match points go begging as fourth-seeded Kasatkina forced a decisive third set.

Collins had lost her two previous matches against Russia's Kasatkina, including a semi-final defeat at the Phillip Island Trophy in Melbourne this year.

But after Kasatkina grabbed the second-set tiebreaker on her fifth set point, Collins, ranked 36th in the world and projected to return to the top 30 after the victory, was able to settle herself and regain the upper hand.

Collins converted five of her eight break points in the match, breaking Kasatkina at love for a 5-3 lead in the first set.

Three aces in a row and a service winner in the next game gave her the opening frame, and Collins went up an early break in the second.

But when Collins was unable to convert two match points against Kasatkina's serve in the ninth game of the second set, the Russian began to gain ground.

She broke Collins to level the set, and seized a 4-0 lead in a tiebreaker that would eventually feature three more match points for the American before Kasatkina finally levelled the match.

Collins gained the advantage for good with a break for 3-1 in the third, finally sealing the match on her seventh match point.

The exhausted American couldn't even summon a celebratory fist-pump and was checked out by a trainer at courtside before addressing the crowd and hoisting the trophy at the victory ceremony.