US Open: Karolina Pliskova fights back to beat Shaui Zhang in third round

Karolina Pliskova was the losing finalist in the US Open in 2016, when the title went to Angelique Kerber

World number one Karolina Pliskova played down an arm injury after fighting back to beat China's Shaui Zhang in the US Open third round.

World number 26 Zhang had match point at 5-4 in the second set, but Pliskova turned it around to win 3-6 7-5 6-4.

The result means she stays in the race with Elina Svitolina and Garbine Muguruza to end the tournament as number one.

"I feel much better," said the Czech, who had treatment after the second set.

"I did some recovery and just saw the physios and some ice bath and those stuff. Hopefully it will be fine, it just felt a little bit tight during the match."

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Ostapenko felt unwell during the second set and called for the doctor

Latvia's French Open champion Jelena Ostapenko, seeded 12th, went down 6-3 6-2 to Russia's Daria Kasatkina, the world number 38.

"Before the tournament I had some problems like with the throat," said Ostapenko.

"I had to take some antibiotics, but I somehow tried to avoid it and try to get ready for the tournament, but today I felt quite bad. I couldn't give my 100%."

Meanwhile, American Coco Vandeweghe won 7-5 4-6 6-4 against 10th seedAgnieszka Radwanska of Poland.

Pliskova, 25, will next face Jennifer Brady in the last 16, after the American beat Monica Niculescu of Romania 6-3 4-6 7-6 (7-3).

She must repeat her run to the final of 12 months ago, at the least, if she is to remain at the top of the rankings.

Ukrainian fourth seed Svitolina beat American Shelby Rogers 6-4 7-5 on Saturday to progress, while Spanish third seed Muguruza plays Petra Kvitova on Sunday.

"I feel pressure," said Pliskova. "I just want to win. I know all the opponents are behind me, so I should win every match, which is tough."

The Czech had to call for the trainer before the start of the third set and received lengthy treatment on her right forearm.

She returned to court and was immediately broken by Zhang, but the 28-year-old was unable to get past Pliskova in the decider.

Elsewhere in the women's draw, Lucie Safarova of Czech Republic beat Japan's Kurumi Nara 6-3 6-2.

Vandeweghe won an epic match with Radwanska that lasted two hours and 55 minutes