Two of the top-ranked Americans in the field at the San Diego Open advanced to the quarterfinals with straight-set wins Wednesday evening.

Danielle Collins backed up an opening win against No.7 seed Caroline Garcia with a 6-2, 6-4 win over Martina Trevisan, before No.4 seed Jessica Pegula closed out the night under the lights with a 6-3, 6-1 win against fellow American CoCo Vandeweghe. 

In her first match of the week, Pegula needed 69 minutes to defeat Vandeweghe and won 12 of the last 14 games after falling behind an early break, at 2-0. The win clinches Pegula's qualification for the singles field at the WTA Finals in Fort Worth, Texas, which begins on Oct. 31. 

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Revenge served for Pegula: The victory was also a measure of revenge for U.S. No.1 Pegula, who lost her only prior meeting against Vandeweghe earlier this year in Charleston in three sets. Pegula said her game plan coming into the rematch was simple.

"When she's on with her serve and her returns, it's really tough," Pegula said. "My goal was just to try and attack and put pressure on her serve when I got the chance.

"On my serve, I thought I just had to serve smart and be ready for a big return. She's got so much easy power, so sometimes she can put a lot of pressure on you, so I was just trying to focus on those two things."

It showed in the stat line: Pegula hit 11 winners to only two unforced errors and won 78% of the points played behind her first serve.

San Diego: Collins beats Trevisan to reach quarterfinals

Adjustments the name of the game: Collins' effort against Roland Garros semifinalist Trevisan was a touch more complicated after she blitzed to a 5-0 lead. Though she broke Trevisan's serve seven times in 10 opportunities, she failed to serve out each set.

Trevisan actually had more break point opportunities than Collins, the 2022 Australian Open runner-up, but converted only four of the 13 chances. 

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"She's never going to give up," Collins said. "We're playing professional tennis out here, so at 5-0, I knew that she was going to probably end up doing something a little bit different and try to make some adjustments with her game. Nobody goes down easy in these matches and she certainly made those adjustments and tried to push me back a little bit more, and I needed to make adjustments within my game technically.

"Sometimes that happened and sometimes that didn't so that was a little bit frustrating for me today but, ultimately, I think the competitiveness and the fiery personality that I have inside pushed me to the finish line."

Up next: Pegula will next face either Madison Keys or No.8 seed Daria Kasatkina, while Collins is the next foe for either No.2 seed Paula Badosa for qualifier Louisa Chirico.