Alexander Zverev lashed out at Martina Navratilova after the 18-times Grand Slam champion said he had played "pat-a-cake" tennis at times during his victory over Borna Coric in the quarter-finals of the US Open.
The German fifth seed was 6-1 4-2 down early in his contest against the Croatian before rallying to win in four sets and reach his second Grand Slam semi-final of the year.
The 23-year-old bristled when he was told that Navratilova had said in TV commentary that he would never win a Grand Slam playing the way he had.
"Maybe she should look at my record against the big guys," he said.
"Maybe she should look that I'm positive against Roger (Federer). Maybe she should look that.
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"I've beaten Novak (Djokovic) on multiple occasions in big matches and finals. And I'm in the semi-finals, and sometimes not playing your best and finding a way is more important than playing your best.
"But she's a Grand Slam champion, as well, multiple Grand Slam champion, she's respected, but her opinion right now does not matter to me."
Navratilova later clarified that her comment had been about how unaggressive Zverev, who is better known by the Russian diminutive Sasha, had been during his slow start.
"Nothing like posing a question in press conference without context," she posted on Twitter.
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"I said Sasha needs to play like he did in the 4th set, not the way he played the 1st 2 sets. It's that simple. But yeah, nice journalism, whoever asked the question. I would have answered the same way Sasha did."
Zverev, who plays Spaniard Pablo Carreno Busta in the last four, said he had changed the way he approached the Grand Slams after failing to get past the last eight in his first 18 attempts.
"I wanted it too much. I was trying too hard in Grand Slams, as well," he said.
"I needed to learn how to deal with that pressure. I needed to learn how to deal with those expectations of myself. It took me a little bit of time but now I'm in the semi-finals of the US Open and I definitely don't want to stop here."