NEW YORK, NY, USA - No.14 seed Elise Mertens became the first 2020 Western & Southern Open semifinalist in style, outmanoeuvring qualifier Jessica Pegula with her signature brand of smart tennis for a 6-1, 6-3 win in one hour and four minutes.

Prague runner-up Mertens is one of two players who have translated a final run in the European clay WTA Tour resumption into strong form in the New York bubble - the other being Palermo finalist Anett Kontaveit - and she was very much in her groove in today, smothering first-time Premier 5 quarterfinalist Pegula to reach the biggest semifinal of her own career since the 2018 Australian Open.

"Adapting from clay to hard was definitely a difficult one," said Mertens afterwards. "Especially the first day, because my first hard court practice was on Wednesday and I had to play on Sunday. But I managed it well, playing against different opponents, different ball strikers. Trying to focus on myself a lot more than on my opponent."

In a 21-minute first set that flashed past as quickly as Mertens tracked down shots, an increasingly frustrated Pegula found that there were all too few places on the court where she could place the ball out of the Belgian's reach. A putative overhead putaway was reflexed back to elicit a Pegula error; a deep groundstroke to the far corner only set Mertens up for a pinpoint lob winner. The World No.22 was even able to speed up to a short net cord to flick a backhand winner off it.

Mertens was also near-impregnable on serve, conceding only two points behind her delivery in the first set and winning all nine on her first serve. Consequently, she was free to put the Pegula serve under continuous pressure, breaking three times as the American began striking out rather wildly and sealing the set with a deep backhand return that her opponent could only put into the net.

"I started really well," assessed Mertens afterwards. "Service was working. She's kind of a hard hitter, so I tried to put a lot of balls back in the court. But I think it was the key with depth so she couldn't make those strikes, those winning points.

The US Open quarterfinalist continued to dominate as the second set got under way, with her dropshots and lobs particularly on point as she chipped away at Pegula's 40-0 lead in the second game to break once again. A lapse into passivity up 2-0 cost Mertens, allowing Pegula to carve out triple break-back point - and though the 26-year-old would ultimately take the third, she needed to come out on top of a marathon rally to do so after Mertens had saved the first two with her most brilliant lobs of the day.

In any case, Mertens, previously a Cincinnati quarterfinalist in 2018, would display supreme matchplay awareness to swiftly rectify her tactics, immediately beginning to step inside the baseline and hit through her groundstrokes once more. The reigning US Open doubles champion was also unhesitating about coming forward, with a silky volley paving the way for another crucial break of the Pegula serve from 40-15 down for a 5-3 lead.

The court speed at the USTA Billie Jean King National Tennis Center had been a factor, according to Mertens. "You definitely have to push yourself to play aggressive all the time, because it's a really fast surface," she explained. "It's faster than last year, definitely. But also, the balls stay lower. You really have to go in your legs and get those balls back, staying balanced... if you're on the run."

Not that different surfaces ultimately bother the ever-versatile Mertens. "I don't know what kind of surface I like the most," she laughed. "I think after a few days, I'm like, oh yeah, this is good - but I don't know, actually. But I try to adapt fast, and that's was I was trying to do."

Though Pegula had found something of a groove on serve in the second set, baseline exchanges still tended to end with the last home hope over-pressing - she would finish with 25 unforced errors to only nine winners - and despite valiantly clinging on with some brave net rushes of her own, it wasn't enough to prevent Mertens from sealing her first Premier 5 semifinal on her second match point with her third ace of the day.

Next up for the 2019 Doha champion will be either No.4 seed Naomi Osaka or No.12 seed Anett Kontaveit. "Anett played a lot of matches since the comeback of tennis, so I think she has a lot of confidence," noted Mertens. "It's going to be difficult either way because Naomi can strike the ball really well, can get those angles in. Especially when her first serve is going, it's going to be difficult. I think I will focus on my game, what I can improve from this one to the next one. Yeah, try to stay focused and in the bubble."

2020 Cincinnati highlights: Mertens speeds past Pegula to make semis