NEW YORK, NY, USA -- Defending champion and World No.1 Naomi Osaka of Japan is now 10-0 in her last ten US Open matches after fending off the challenge of American teenage sensation Coco Gauff, 6-3, 6-0, under the lights of Arthur Ashe Stadium on Saturday night.

No.1 seed Osaka, who followed up her US Open title by winning her second Grand Slam title at the Australian Open in January, improved to 17-0 over the last three hardcourt major events after her 65-minute win over 15-year-old wildcard Gauff.

"I'm just out here trying my best," a jovial Osaka said in her post-match press conference. "I'm just going with the flow at this rate. I've never defended a Grand Slam before. We out here, you know. We're just having fun."

Read more: 'She proved that she's a true athlete' - Gauff reflects on Osaka exchange at US Open

After a close start, Osaka reeled off the final eight games of the match, converting six of her seven break points and winning three-quarters of points on her first serve. The top seed's high-voltage game was on song for most of the match, which she finished with 24 winners to 17 unforced errors.

"I haven't played a night match on Ashe since last year," said the reigning champion. "I felt the atmosphere was, of course, going to be very different. I think the day crowds and the night crowds are very different here. I mean, everyone was very into this match, I think. For me, I just wanted to see how [Gauff] played. I think that was the biggest thing."

Gauff, who is at a career-high ranking of World No.140 after a run to the fourth round of Wimbledon which captivated tennis fans globally, started strong and matched the World No.1's solid service speeds throughout, but was ultimately undone by 24 unforced errors, compared to eight winners.

Osaka got off to a hot start, cracking two backhand winners and two aces to hold in the first game, then earning an early break for 2-0 after Gauff double faulted on break point. Gauff, however, quickly established a foothold, slamming back-to-back aces of her own to get on the board at 3-1, then breaking back for 3-2 after the Osaka error count rose.

That game started a run of four consecutive breaks of service, where the rallies favored the bold returners as each player wobbled when putting their second serves into play. When the dust settled, Osaka led 5-3 and served for the set, although she had dropped three of her last four service games.

Osaka faltered at first, pushing a backhand wide and hitting a double fault to fall behind 0-30, but two netted errors by Gauff in the next two points helped the No.1 seed’s cause. Osaka then steeled herself and blasted a backhand winner to create a set point for herself, which she claimed after Gauff hit a backhand error into the net to end the opening stanza.

Read more: ‘Coco, I think you’re amazing’ - Naomi Osaka and Coco Gauff’s emotional moment after US Open clash

Osaka did not let up in the very start of the second set, knocking off an atypical drop volley winner to earn two break points in the first game, then watching Gauff cede the break to her with her third double fault of the match.

Gauff, however, continued to fight, attacking returns aggressively and earning three break points in the very next game. However, the defending champion methodically whisked all of those opportunities away, and despite two thunderous returns by Gauff after deuce, Osaka tracked down everything the teenager threw at her and held on for 2-0.

It was overall smooth sailing for the top seed from then on, as Osaka broke for 3-0 after Gauff’s errors piled up, and held for 4-0 after a close game by slamming an ace on game point. Osaka cruised home from there, and the two stars shared a hug and a lengthy chat at the net after their blockbuster match ended in favor of the defending champion.

Osaka persuaded Gauff to share the on-court post-match interview with her. "I was just thinking, it would be nice for her to address the people that came and watched her play," Osaka explained. "They were cheering for her. I mean, for me, it was just something that was, I don't know, instinctive I guess." 

"I literally was training at the same place as her," Osaka continued. "It was always just us putting in the most amount of hours. She was always with her dad just practicing. Honestly, I think she was practicing more than me."

"It's crazy to me to see how far she's come in such a little amount of time," the World No.1 added.

Osaka will now meet No.13 seed Belinda Bencic of Switzerland in her next match. Bencic advanced to the fourth round after No.21 seed Anett Kontaveit of Estonia withdrew from their scheduled third-round tilt due to a viral illness. Osaka won their first meeting at a Challenger in Alabama way back in 2013, but Bencic has been the victor in their two WTA meetings, both coming this season.

"Playing [Bencic] is always super challenging," Osaka admitted. "I'm unsure if I've ever won a match. I know that I lost the two times we played earlier this year. For me, I just expect a fight. She doesn't really ever give up. She kind of fights for every point. I know that's going to be a really difficult match for me."