MOSCOW, Russia - An intriguing stylistic contrast at the Kremlin Cup saw No.5 seed Dayana Yastremska eliminate defending champion Daria Kasatkina 6-1, 6-4 in the first round after one hour and 20 minutes of play.

"I'm really pleased with my level of tennis today," said a satisfied Yastremska afterwards. "Particularly when she started to come back in the second set. It was important for me to show my best game here today, and I enjoyed the challenge of coming up against the defending champion."

Yastremska was especially pleased with her game given her recent global travels. "It's just my second day here after a long trip from Asia, and I think my body is still trying to acclimatise," she explained. "I've been travelling so much recently that in my mind I'm still somewhere flying! I'm still a little bit sleepy, but I'm OK."

The first meeting between 19-year-old Yastremska and the home favorite saw the power of the former blitz through the latter, with the Ukrainian striking 25 winners to 31 unforced errors - as well as demonstrating how much she has added to her game over the course of her first full year on the WTA Tour, winning 11 out of 14 points at net.

During an impeccable opening set, Yastremska was able to rein in her power to conjure up sharp angles and judicious dropshots - while her net play was coolly controlled and efficient as she leapt out to a 5-0 lead.

Kasatkina, meanwhile, has had a lean year, compiling just a 12-20 win-loss record coming into Moscow - and despite putting together an uptick in form in her last tournament to reach the Beijing quarterfinals, contributed significantly to shutting herself out of the set. Eleven unforced errors to only four winners didn't help, but most problematic were four ill-timed double faults: one squandered a point for an opening hold, one set up a break opportunity for Yastremska in the fourth game and the remaining two came down break point in both games.

The second set opened in much the same unfortunate vein, with Kasatkina serving a fifth double fault down break point yet again in the first game - but off the ground, the Russian was beginning to tighten up her game as Yastremska came down from her high.

Maintaining greater depth, Kasatkina began to draw a series of errors from her opponent - and, competing valiantly, seemed to have won a key mental battle when she came through a six-deuce tussle to break the Hua Hin and Strasbourg champion for 4-2 - despite seeing two of her first five break points evaporate on dead net cords.

But Yastremska came roaring back with her highest level of play yet. Winning the point of the match with a remarkable get off a Kasatkina volley, Yastremska powered through a brace of returns to break back immediately - and then began to run rampant, blitzing three consecutive backhand winners down the line to capture Kasatkina's serve again for 5-4.

The Wuhan quarterfinalist's run of 12 consecutive points came to an end with a double fault of her own as she served for the match - a game that turned into a minor adventure as her first two match points came and went, but which Yastremska eventually sealed by firing consecutive winners off each wing to take her overall total to 25. Next up for the youngster will be Belgian qualifier Kirsten Flipkens, who moved past Russia's Natalia Vikhlyantseva 6-3, 6-2 in one hour and seven minutes.