Naomi Osaka needed to work harder than might have been expected on Friday to escape potential danger from Marta Kostyuk, holding off the rising Ukranian teenager 6-3, 6-7(4), 6-2 in the US Open third round.
The Japanese fourth seed claimed victory after nearly two and a half hours playing with a massive strapping on her left leg.
The former world No. 1 and 2018 Open champion managed to dominate until the 137th-ranked youngster earned her first break chance of the afternoon in the 16th game.
“My biggest takeaway from her game is that she didn’t back down from me or from the speed of my ball, which for someone that young is kind of amazing.” Osaka said.
“In the third set towards the end I feel like physically I was better, and I was, of course, more experienced.
“But I feel like she’s definitely going to be dangerous.”
Osaka moves on with a match against Anett Kontaveit, who beat Magda Linette of Poland 6-3, 6-2,
Eighth seed Petra Martic broke new ground as she booked the first of the fourth round places 6-3, 6-3 over Russian Varvara Gracheva.
The Croat is into the second week of the Open for a second consecutive year and will next face Yulia Putintseva, who defeated Aliaksandra Sasnovich 3-6, 6-2, 6-1.
2016 winner Angelique Kerber stormed to another straight-set win, reaching the fourth round over Ann Li 6-3 6-4.
Germany’s three-time Grand Slam champion fired 36 winners in the drubbing which took 78 minutes over the American.She returned to the second week here for the first time since her trophy run four years ago.
“Four weeks ago, I didn’t think we would be in New York,” she said. “Now that I’m here, I’m feeling great,
“I was a late decision but a good one. I’m having a lot of fun. I’m happy to be in the second week, I’ve decided to just focus on the court.
“I’m concentrating point-by-point, I just want to concentrate with what is happening on the court.
“I’ve worked so hard in the last weeks, I want to show what I can do on the court.
American Jennifer Brady reached the fourth round here for a second time after 2017, helped by 18 winners and just nine unforced errors in her 6-3, 6-3 knockout of France’s Caroline Garcia.