San Diego, Oct 13 (IANS): American Jessica Pegula booked a spot in the quarterfinals of the San Diego Open, and a berth at the WTA Finals at Forth Worth, with a straight-set win against compatriot CoCo Vandeweghe.

The No.4 seed Jessica Pegula closed out the night under the lights with a 6-3, 6-1 win over fellow American CoCo Vandeweghe while another American also reached the last eight when 2022 Australian Open finallist Danielle Collins defeated Italy's Martina Trevisan 6-2, 6-4.

In her first match of the week, Pegula needed just 69 minutes to defeat her former Top 10-ranked compatriot and won 12 of the last 14 games after falling behind an early break at 2-0. She also made personal history -- the win clinches Pegula's qualification for the singles field at the WTA Finals in Fort Worth, Texas which begins on October 31.

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, said a report on the WTA Tour website.

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

"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."