A cramp-stricken Kyle Edmund was dumped out of the US Open in the first round, losing 4-6 6-4 7-5 6-1 to Italian veteran Paolo Lorenzi.
Lorenzi, 36, has a good record in New York having taken a set off Andy Murray in the third round in 2016 before reaching round four last year.
However, it still looked a good draw for Edmund, now a solid top-20 player and the 16th seed.
The British number one has not shown the form he would have liked on the North American hard courts, winning only three matches in four tournaments, but had the better of three straight breaks of serve to start the match before taking the first set.
But, gradually, Lorenzi and the punishingly hot and humid conditions began to get the better of Edmund.
He was broken to lose the second set and the same thing happened in the third, this time from 40-0.
Most read in Sport
By now, cramp had started to set in and Edmund called the trainer for some salt tablets.
He was struggling to move, though, hopping around on the baseline as his calves tightened.
A series of double faults from Lorenzi kept a wincing Edmund in the set, but the longer it went on, the more the momentum swung towards the unseeded Italian.
Lorenzi sent down eight of his 20 aces in the final set as Edmund became more restricted, closing out the victory in the little resistance coming back from the Brit.
Edmund did not win a game until 5-0 in the fourth set as he suffered a first-round loss at a slam for the first time since Wimbledon 2016.