NEW YORK, NY, USA - Former World No.1 Naomi Osaka closed out the first day of the 2020 US Open with a decisive win over countrywoman Misaki Doi, advancing, 6-2, 5-7, 6-2 to edge into the second round.

"It was very difficult," she told Rennae Stubbs during her on-court interview. "I kind of expected it because of the first round nerves, and she's also a very tough opponent. I knew there was a chance it could get really long. I just have to see what happens tomorrow and how I feel."

The No.4 seed was playing her first match since withdrawing from the Western & Southern Open finals over the weekend due to a left hamstring injury, but showed few ill effects as she defeated Doi in two hours and two minutes under the lights.

"I felt like my ball toss could have been better, but it did what it needed to do on the very important points, so I can't be that mad. I still have to practice."

Champion at the USTA Billie Jean King National Tennis Center in 2018, Osaka arrived in New York a week early to play her first tournament since the Australian Open and overcame an impressive field before injury precluded her participation in the championship match against fellow former World No.1 Victoria Azarenka. 

Emerging for her first round wearing a face mask in tribute to Breonna Taylor against Doi, a dangerous floater who has challenged the likes of Angelique Kerber and Karolina Pliskova on the sport's big stages - holding a match point against the former before the German went on to win the 2016 Australian Open - Osaka held off her compatriot's impressive lefty swings with some audacious hitting of her own, striking eight winners and breaking serve twice to serve out the opening set at love.

"I have seven masks," Osaka clarified. "It's quite sad that seven isn't enough given the number of names. Hopefully I'll make the final and you can see them all."

The beginning of the second set saw the 29-year-old Doi, who was yet to win a WTA main draw match in 2020, capitalize on a dip in Osaka's form to edge within a game of leveling the match at 5-2. 

Osaka found a second gear from there, breaking Doi as she served for the set, and held three break points that would have saw her serve for the match.

Doi steadied and held on after a baseline rally, and reversed a 40-15 deficit to even the match at one set apiece.

With the clock ticking close to midnight, Osaka opened the ensuing decider with a break and saved two break points in the following game to consolidate a 2-0 advantage. While Doi kept fighting, her resolve appeared to wane as Osaka stepped up her game one last time.

The World No.9 earned a double-break lead and securing victory with a powerful backhand that forced a Doi reply into the net.

In all, she struck a solid 25 winners to 38 unforced errors, and won 76% of points behind her first serve while converting five of 11 break point opportunities. While Doi made the same number of errors, she could manage just 17 winners of her own, and converted two of eight break points.

Up next for Osaka is the always-dangerous Camila Giorgi, who survived an epic three-setter against Alison Van Uytvanck earlier in the evening. The Japanese star won their only prior meeting at the Toray Pan Pacific Open back in 2018.

"I've played her before. She's very unpredictable for me. I just have to be on my toes."

2020 US Open highlights: Osaka dispatches Doi