Naomi Osaka overcame a huge test to reach the second week of the US Open for the third consecutive year, with Japanese edging past teenager Marta Kostyuk in three tough sets to progress.

Osaka impressed in her second round match against Camila Giorgi on Wednesday, dropping just three games to the Italian in a comfortable victory, though it was hard not to notice the heavy strapping on her left hamstring. The injury forced her to withdraw from the Western & Southern Open final last weekend, and she remained coy in press in regards to it.

“The leg tape, I didn't do so well in my last match because -- I don't know. Should I be telling you this? Yeah, I guess you could say it's preventative. Yeah, let's just go with that,” Osaka commented rather evasively after her second round match, elevating concerns that she may be far from full fitness.

Kostyuk in action (Image: Al Bello)
Kostyuk in action (Image: Al Bello)

It appeared early on that Osaka was unhampered by any injury with early pressure seeing her break the Ukranian in the fifth game. Kostyuk showed why she is considered one of the brightest prospects on tour with some aggressive play, saving three break points to hold down 4-2, though the fourth seed was too solid overall and broke for a second time on her third set point to claim a fairly straightforward opening set

Serving continued to be an issue for the Ukranian early in set two, though was crucially able to save the seven break points she faced across her first two service games. Errors were creeping into Osaka’s game and Kostyuk took advantage, breaking for the first time and holding for a 5-3 lead. She missed a set point on the Japanese’s serve and Osaka broke with some impressive tennis as she served for the opening set, though forced a tiebreak and took control early on; Kostyuk took her second set point to force a decider.

Image: Al Bello
Osaka overcame her toughest test so far to reach the second week (Image: Al Bello)

Kostyuk looked full of confidence heading into the decider and, up 2-1, held five break points to take control of the decider. However, some aggressive from Osaka saw her stay level, and the Japanese pounced on some nervy serving from the teenager to secure the opening break of the decider. Osaka held to love and was handed a second break by Kostyuk, who had seemingly lost confidence in her game after missing those break point opportunities. The fourth seed held comfortably to seal a hard-fought 6-3, 6-7(4), 6-2 victory.

The Ukrainian, currently ranked 137th in the world, impressed at times and showed signs of a promising career, though it was ultimately Osaka's experience that proved to be the key in this encounter; the five break points she saved early in the decider proved to be a 'sliding doors' moment for this contest.

The fourth seed will next face either Anett Kontaveit, who she beat in three tight sets last week, or Magda Linette. Both are aggressive ballstrikers capable of providing another test for the Japanese as she looks to win a third Grand Slam title.