From boardroom chic to battling win, Osaka reaches US Open last 16

She looked on course for a business-like win after the first set but was dragged into a battle in the third, where she had to fight ​through the Achilles niggle to advance. "I wouldn't say it's a huge injury," Osaka.

"I'd say it's this ​ongoing problem that I've had since the grass season. "I don't know why it hasn't gone ⁠away. I feel I've done a lot of things in order to make it better, but maybe the time ​off wasn't enough.

I'm not really sure what the reason is, but the medical timeout was to address that. "You know, ​she massaged my leg and stuff, so that seemed to help, and gave me Tylenol.

"The 28-year-old, a two-times champion at Flushing Meadows, reeled off three games in succession to take a 4-1 lead in the first set under the lights of Louis Armstrong Stadium, clinching ​it with a battling hold thanks to a string of booming serves.

Osaka pushed the 23rd seed hard at the ​start of the next set with some heavy hitting from the baseline before pouncing with a break in the third game, only ‌to surrender ⁠the lead by dropping the next two games.

"Honestly, I can't believe I won this match," Osaka said on court after sealing victory, thanking the crowd for the energy they provided. "There was a certain point where I put my heart on the court and kept trying in every point.

Thank you so much, but honestly, I'm shocked I won. I'm not ​going to lie. "After levelling the ​match to force a decider, ⁠Mertens capitalised on several unforced errors by a frustrated Osaka to gain the upper hand, but there would be another momentum shift in the match after a medical timeout ​for the Japanese player.

"I didn't play amazing and it was getting me down, sorry about ​my behaviour, ⁠for the little kids watching," said Osaka, who threw her racket to the floor at one point. "This is my favourite tournament.

I wanted to play well in front of you. I'm just that glad I have the opportunity to play another match. "I ⁠thought I ​was going to be ok, but clearly I was shaky.

"After recovering ​a break late on, Osaka fired a huge ace to take a 6-5 lead and revved up her forehand in the following game to complete ​the win and earn a meeting with Elena Rybakina in the next round.