World No.1 female tennis player Iga Swiatek has raised eyebrows with a strange tactic at the US Open.

She beat unseeded American Lauren Davis in straight sets, 6-3, 6-4, but there was one moment in the second set that left tennis legend John McEnroe baffled.

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Leading 2-0 in the second, Davis came to the net and waved her arms furiously in the air in an attempt to put Davis off.

David was left unfazed, but McEnroe slammed Swiatek for the move.

“I don’t know about that,” he said.

“I don’t think that’s legal … that is a little bit below the belt.

“The last time I saw that was when I was playing in 1986, I believe, and (Mansour) Bahrami came in and served, and put his hands wide open and said, ‘hit me’. And my partner Peter Fleming hit him in the forehead. And I said, ‘He’s a joke, this guy! I don’t understand what he’s doing. This is serious’.

“And Bahrami was like ‘good shot Peter, good shot!’ He loved it. I don’t think Swiatek has to do that.

Iga Swiatek is the world No.1. Credit: Robert Prange/Getty Images

“She’s so good it seems … but she’ll learn. She’s 21.

“That’s something that you do in juniors tennis. That’s not something that you do if you’re world No.1.”

Fans followed McEnroe’s lead, adding to the choir of condemnation for the Polish star.

Swiatek was 1-4 down at one stage in the second set, but came home strong to win five games in a row and storm into the round of 16.

“I couldn’t find my rhythm today,” Swiatek said in her on-court interview after the match.

“I’m trying to enjoy every match, even when it’s not perfect. Just trying to go for it. Trying to find solutions in every situation”.

Swiatek went on a blistering 37-match winning streak earlier this year to claim titles at Roland Garros, Doha, Indian Wells, Miami and Rome but has lost four matches during the hard-court season.

After three consecutive straight-sets wins in New York, the Pole next faces young German Jule Niemeier, who has backed up her run to the quarters of Wimbledon by making the last 16 on her main-draw debut here, beating China’s Zheng Qinwen 6-4 7-6 (7-5).

Serena takes final bow after Aussie’s US Open stunner.

Serena takes final bow after Aussie’s US Open stunner.

Veterans Kvitova, Azarenka enjoy Open wins

Elsewhere at Flushing Meadows, some of the veterans of the women’s game wound back the clock to take stirring victories.

Petra Kvitova took inspiration from Serena Williams to defeat Spain’s Garbine Muguruza and reach the fourth round.

A tense clash between the two former grand slam champions saw Kvitova save two match points to force a deciding tiebreak, before eventually winning on Saturday 5-7 6-3 7-6 (12-10).

Petra Kvitova wound back the clock at the US Open. Credit: Frey/TPN/Getty Images

“I didn’t want to go out of this tournament, so I was just there hanging somehow,” the Czech, who was in tears at the end, said.

“She (Muguruza) was playing aggressively, as well. Me too … So I was trying to go for it with these first serves or for aces”.

Kvitova next meets American eighth seed Jessica Pegula after she defeated China’s Yue Yuan 6-2 6-7 (6-8) 6-0.

“Petra is so hard to play. I feel like when she’s on, she blows you off the court,” Pegula said.

“And then sometimes she can be off .. She’s a fighter. When it clicks, it’s really difficult”.

With AAP

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