Swiatek struggles into US Open fourth round

But Swiatek clawed her way back into the contest to complete a 7-6 (7/2), 6-4 victory on the Arthur Ashe Stadium court.

Even Swiatek was at a loss to explain how she turned around her poor start.

"Oh my god I don't know -- Anna was playing great, she was playing all these risky balls in," she said. "I just wanted to make less mistakes. I felt like I was playing good but in the last shot I just couldn't finish it.

"I just focused on simple things ... I felt like I had nothing to lose because I was losing pretty bad. So in the end I just went for it because what else can you do?"

Swiatek looked out of sorts almost from the outset, struggling to find fluency on serve and making a stream of unforced errors.

She went 2-1 down after being broken in the third game, and Kalinskaya soon had Swiatek in trouble again in the fifth.

A nervy double-fault at break point from Swiatek handed the Russian a 4-1 lead, which duly became 5-1 when she held in the next game.

But serving for the set at 5-2 up, Kalinskaya suddenly froze to let Swiatek back into the match, squandering four set points before being broken.

Swiatek broke again to level it at 5-5 and the momentum appeared to be with the Pole.

Yet there was another twist as the two players swapped breaks of serve to set up a tiebreak, which Swiatek won comfortably.

The second set opened with both players again trading breaks of serve. The set went with serve until Swiatek seized the initiative in the ninth game to break for a 5-4 lead.

A whipped Swiatek forehand set up match point, which the Pole converted when Kalinskaya yanked a return wide.

Swiatek will face Russian 13th seed Ekaterina Alexandrova in the fourth round on Monday.

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