Former World No. 1 John McEnroe has claimed top swiss players Stanislas Wawrinka and Roger Federer were involved in a locker room stoush after their ATP World Tour semifinal in London on Friday night.

“Something went on in the locker room between Federer and Wawrinka and it extended long into the night,” McEnroe said while commentating for ESPN.

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McEnroe would not elaborate on the nature of the conflict, but it followed a particularly tense on-court showdown during Federer’s 4-6, 7-5, 7-6 (8-6) victory over Wawrinka.

Late in the third set, Wawrinka appeared to lose his temper with someone in Federer’s box and was filmed allegedly saying, “she did the same thing during Wimbledon”.

There is speculation Wawrinka was talking about Federer’s wife, Mirka, making noise before his service motion.

When Wawrinka was asked about the incident in a post-match interview, he was dismissive.

“Not much. Nothing special. Tense match. It’s never easy,” he said.

Meanwhile, Federer gave no sign of stress after the match, telling reporters the match was challenging but rewarding.

“It’s very hard, obviously, against Stan,” Federer said.

“It’s been a long season for both of us. I’m happy we’re able to play such a good match.”

Man with access to TV footage assures me that Mirka was the target for Stan outburst as she was talking after the serve was hit

— Simon Briggs (@simonrbriggs) November 16, 2014