American teen Coco Gauff and defending champion Victoria Azarenka notched straight-set wins Tuesday to kick off their 2021 Western & Southern Open campaigns.

Gauff stormed past crafty Hsieh Su-wei of Chinese Taipei 6-1, 6-2 setting up a showdown with No.2 seed Naomi Osaka.

In their first meeting, 17-year-old Gauff fended off the unorthodox patterns of 35-year-old Hsieh to claim a spot in the second round of the event for the first time in her career, after exactly an hour of play.

That hour of action, however, was split into two nearly equal-sized chunks by a rain delay of about three hours, with Gauff leading 5-0 when the precipitation came. Nevertheless, the American continued to excel even after the lengthy pause.

Gauff dismisses Hsieh in Cincinnati opener: Highlights

Stats of the match: Gauff had 20 winners to 16 unforced errors, while Hsieh's 11 winners were undone by 19 unforced errors. Gauff also took advantage on break points, converting five of six on the day.

"I think I did well just focusing on my side of the court," Gauff told the press after her win. "She hits a crazy shot, and trying to not let that get into my head, because she's talented and she will hit great shots."

Key moment: After being dispatched with ease in the first set, Hsieh made a momentary charge back into the match in the second set. Hsieh broke Gauff for the first time to get back on serve at 2-2, and despite dropping serve again, had two more break points at 3-2 following a Gauff double fault.

But that is where Gauff put the brakes on Hsieh's comeback, slamming two aces to get to deuce, then firing two more unreturned serves to seal the 4-2 lead. The teen was not challenged again as she eased to the straight-set victory, wrapping up the match with her 10th ace.

All-star clash next: Gauff and Osaka will be facing off for the third time, with each of their meetings taking place at a prestigious hardcourt event.

Osaka defeated Gauff in the third round of the 2019 US Open, 6-3, 6-0, but at the next major, Gauff got her revenge in the same round, beating Osaka 6-3, 6-4 in the third round of the 2020 Australian Open.

"I definitely did learn a lot from both matches [against Osaka], actually," Gauff said. "The second match, I learned that I can perform well under the pressure, and that I do have a lot more fun on the court when I try not to focus on the expectations of other people and myself, whereas I didn't really find that I guess balance until that Australian Open match." 

Reigning champ Azarenka holds off Samsonova surge

No.14 seed Azarenka of Belarus, who won the title when the event was played in New York last season, slid past big-hitting Russian Liudmila Samsonova 6-2, 6-3 in their first-round battle.

Two-time champion Azarenka, who also won the 2013 title in Cincinnati, quelled a late surge by the rising Russian to earn victory after a relatively routine 1 hour and 9 minutes of play.

It was a measure of revenge for Azarenka, who fell to Samsonova during the Russian's breakthrough grass-court season earlier in the summer. Samsonova beat Azarenka en route to her maiden WTA singles title on the lawns of Berlin, then reached the round of 16 at Wimbledon as a wildcard.

On the hardcourt of Cincinnati, Samsonova out-winnered Azarenka by 15 to 10, but the powerful Russian was undone by a whopping 32 unforced errors. Former World No.1 Azarenka took advantage and converted five of her seven break points in the win.

Azarenka was steamrolling to victory, leading by a set and 5-0 before the Samsonova power game clicked into gear and garnered the Russian three games in a row.

At 5-3, Samsonova held two break points to get back on serve, but outstanding groundstrokes, one from each wing, pulled Azarenka back to deuce. The defending champion held on from there to clinch the win and a meeting with Alison Riske in the second round.

Rybakina stops Stosur

In another match which was affected by the three-hour rain delay, Elena Rybakina of Kazakhstan ousted former US Open champion Samantha Stosur of Australia 6-3, 6-3 to reach the second round of the Western & Southern Open for the first time in her two career appearances.

It took Top 20 player Rybakina 70 minutes to knock out the former World No.4. Rybakina, who finished in fourth place at the Olympics, won a staggering 90.5 percent of her first-service points, and was never broken in the encounter.