Andy Murray crashed out of the US Open in the last 16 after the British number one was beaten in four sets by South Africa's Kevin Anderson.
The defeat marks Murray's worst performance at a grand slam in five years and brings an end to his run of 18 consecutive quarter-finals at major tournaments.
Here, Press Association Sport, takes a closer look at what went wrong.
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1. Busy schedule
A hectic schedule has almost certainly taken its toll on Murray, who has played competitions in five out of the last six weeks. After reaching back-to-back semi-finals at the French Open and Wimbledon, the Scot used every ounce of energy left in Britain's Davis Cup tie against France, when he won three matches in three consecutive days.
Since then, he has played tournaments in Washington, Montreal and Cincinnati, and the US Open may have been a bridge too far after a strenuous three months.
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2. Early rounds
If Murray was tired coming into the tournament, there was no respite in the early rounds where he was handed a difficult opener against Nick Kyrgios. Murray had to play his best to win in four sets while the hype surrounding Kyrios' recent antics must have been mentally draining.
That was followed by a five-set marathon with Adrian Mannarino, which came in sweltering hot conditions, and needed Murray to come from two sets down to go through. Thomaz Bellucci proved less taxing in round three but Murray began against Anderson with far more mileage in his legs than he would have liked.
3. Louis Armstrong Stadium
Murray has a history of struggling in Flushing Meadows' second largest arena and so it proved again on Monday. Armstrong is tight, which makes it harder to defend, and fast, making it harder to retrieve, particularly against a big-server like Anderson.
Murray's last grand slam exit before the quarter-finals came on the same court against Stan Wawrinka in 2010 and he has since endured struggles there against Marin Cilic in 2012 and Robin Haase last year.
Jonas Bjorkman has been an excellent addition to Murray's coaching team this year but there is no doubt the world number three has missed Amelie Mauresmo, his number one coach who is on maternity leave and did not travel to New York. Mauresmo brings a calm and focus to Murray's preparations and his only dips in 2015 - in February and at the US Open - have come when the Frenchwoman has been away.
Anderson is renowned for his rocket-serves but he proved himself far more than a one-trick-pony against Murray, whom he regularly outmanoeuvred with touch, craft and creativity.
The 6ft 8in South African, ranked 14th in the world, has been knocking on the door of the top 10 for a while - he took Novak Djokovic to five sets at Wimbledon in July - and this victory could be the start of a more consistent spell of competing with the elite.