Thursday 8 September 2016 14:58, UK
Andy Murray's hugely successful year finally took its toll in the US Open defeat by Kei Nishikori, says Sky Sports expert Barry Cowan.
The world No 2 has claimed the Wimbledon title and Olympic gold during a career-best spell, but fell short in the last Grand Slam tournament of the year after a 1-6 6-4 4-6 6-1 7-5 quarter-final defeat to Nishikori.
Murray had been forced to work for a third round win over Paolo Lorenzi and Cowan believes his renowned mental toughness has been pushed to the limit by a relentless schedule.
"I think that Andy's had an incredible run, no doubt his best run ever," said the Sky Sports expert. "But I felt that it was always going to be difficult for him, coming into the US Open, if he had to dig deep emotionally.
"Against Paolo Lorenzi, that was kind of the warning sign. Lorenzi did play very well, but you wouldn't expect Andy to have to dig as deep as he did.
"His intensity - which has been ridiculous these last few months - just was lacking. It showed when he took leads and Nishikori broke straight back. Against a top player like Nishikori, that could be the difference, and it showed yesterday."
The Scot admitted he lost his composure after a malfunctioning public address system let out a loud noise, forcing a point to be replayed while he was 15-40 up on Nishikori's serve.
Murray lost his grip on the match from that game onwards, but Cowan insists he can still look back with pride on his achievements in 2016.
"There are always quirky things that can happen to halt play and obviously that was a really unfortunate incident for Andy, because he did have the momentum at two sets to one," said Cowan.
"Those are the small points that when you're 100 per cent emotionally fresh, that mental edge can give you the difference.
"His level of performance in terms of his tennis, has been extraordinary on the clay, on the grass, and the Olympics. With those two emotional highs, I always thought it was going to be really difficult.
"Yes, obviously he will be disappointed with yesterday, but I think you have to look at the season as a whole as hugely positive."
