Patrick Mouratoglou revealed he knew Serena Williams was destined to fail in her bid for a historic calendar grand slam from the “very first second” they met on Friday.

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Williams’ French coach was cool, calm and collected while the rest of Flushing Meadows was in utter disbelief after Italian Roberta Vinci produced one of the greatest shocks ever to send the world No 1 out and destroy her hopes of becoming the first woman since Steffi Graf in 1988 to land all four majors in one season.

Williams was certainly well off her game and looked a shadow of the player who had rampaged her way through to the last four.

Mouratoglou, however, saw the warning signs flashing before him.

“She clearly played a bad match today, she was moving not as usual, very slow and there was no movement with her lower body so she was always in a bad position to be aggressive and play her attacking game,” said the Frenchman.

“It was clearly a bad day for her. I could see that from the very first second that I saw her in the morning. Usually at slams there are bad days but you need to find a way through and unfortunately she didn’t do that.

“I saw straight away that she wasn’t looking well. There are days when you wake up and simply don’t feel great. This was one of those days.

“It has nothing to do with her opponent, she just wasn’t moving well enough. Maybe playing a player like Vinci after coming up against someone like Venus took its toll because maybe she wasn’t feeling the same pressure, you don’t come to the court with the same intentions.

“She wasn’t feeling well and also she was not mentally aggressive. It’s not all about physical problems. Players sometimes don’t wake up the same way. They are humans.

“Was it the biggest shock I have ever seen? No because it all depends on what Serena does rather than her opponent. Tactically she wasn’t able to work it out and when that starts happening, it’s difficult to turn it around.”

Missing the chance to create history is sure to hurt Williams yet Mouratoglou reckons the agony suffered here will inspire the American, who turns 34 later this month, to go one better next season.

“In a way this could be good – there is still this high goal to achieve. Sometimes bad news is good news,” he added.