NEW YORK, NY, USA - No.20 seed CoCo Vandeweghe navigated a tricky final set to up-end longtime nemesis and former World No.2 Agnieszka Radwanska, 7-5, 4-6, 6-4, to reach the fourth round of the US Open for the first time in her career.
"I'm really happy with getting to the second week," she said in her post-match press conference. "It's a step closer to what I would like to do here.
"My approach hasn't been much different. Maybe a little bit mentally. I've been more selfish with just kind of my time, what I'm willing to do, what I'm not willing to do as far as being an American in New York. For me, I have lots of friends and family. It's, like, kind of pick and choose my time wisely."
Vandeweghe is in the midst of a best-ever season after surging into the semifinals of the Australian Open and the quarterfinals of Wimbledon. In order to clinch her third Grand Slam second week out of the last four, the 25-year-old had to face Radwanska, whom she'd only beaten once in six previous encounters and lost to back at the Rogers Cup in Toronto.
"Aga is a difficult opponent for me. She poses a lot of problem, gets a lot of balls back, and hits a lot of tricky shots.
"It was a tough-fought match. I can't help but to be proud of myself for the way I competed and continued to fight out there. So I think in doing that, that gives me a lot of confidence."
Still, the 2015 BNP Paribas WTA Finals Singapore presented by SC Global champion had yet to reach the quarterfinals at the USTA Billie Jean King National Tennis Center despite stellar hardcourt results throughout her career, bowing out to a big-hitting Ana Konjuh in the fourth round a year earlier.
Alongside new coach and Hall of Famer Pat Cash, Vandeweghe has employed a hyperaggressive gameplan of late, channeling the 1987 Wimbledon winner with multiple forays to the net on Saturday - 49 in total against Radwanska - to ultimately steel past the Pole in just under three hours in front of an enraptured Arthur Ashe Stadium.
"I think Pat gives me a very specific goal of what to do with the energy and fire that I do bring to the court. I think it's worked very well."
The deciding set featured five breaks of serve, but the American won a dramatic eighth game to put her four points from victory, serving it out behind 49 winners to 54 unforced errors.
"I think I'm improving as far as settling in in a moment. Arthur Ashe Stadium is one of the biggest moments in tennis, aside from probably Wimbledon's Centre Court.
"When I play the night match, it's different. It's electric. The stadium's buzzing. It's hard to put into words what it's like where you feel the goosebumps when you hear everything going on, the lights go out, you walk out. It's wild."
A disappointed Radwanska maintained perspective in press, feeling the high-quality match came down to a few points.
"Every set could have ended differently, to be honest," she said. "Sometimes you just need a little bit more luck out there, and I didn’t have that.
"She returned great, as she always does so I knew to expect that, but the serve wasn’t there in the important moments."
Standing between Vandeweghe and a first US Open quarterfinal is Czech veteran and WTA Doubles No.1 Lucie Safarova, who ended the surprise run of Kurumi Nara in straight sets to start the day.
"It's fun to play a lefty," Vandeweghe said. "I like playing lefties. There's not enough of them on tour to really kind of get to play a lot against them.
"I'm excited to have the opportunity to play against Lucie. I know she's a tough competitor. She's former top 10 in the world, finalist at a Grand Slam. She's definitely no slouch at all."