Andy Murray admitted after his demoralising finish to the season in Paris that he had been to the gym only twice in two months after allowing his training intensity to drop away.
Murray had put himself in a strong position against 37-year-old Frenchman Gilles Simon, even serving for the match at one stage. But he went into physical decline before the match had even reached its halfway mark, suffering cramps as early as 2-2 in the second set, and imploded in a 4-6, 7-5, 6-3 defeat that he said was "my fault, my responsibility".
"It's nothing to do with my hip," said Murray, after Monday's night session. "I think just the reality is I need to work harder. I've not really done much since the US Open, like, physically in the gym, or anything. I've done, you know, very, very little. And that's off the back of not doing a training period off the back of Wimbledon.
"From an endurance perspective," added Murray, "that's something that, for a large part of my career, I kind of pride myself on - being there right to the end of the matches, and being able to maintain a high level physically. I haven't done that at all since … well, in any of the tournaments since Wimbledon really, except New York. That needs to change.
"The last few months, from that side of things, have been really, really disappointing. It's my fault. It's my responsibility. I will take that into the off-season, and make sure that it doesn't happen to start the year."
Cramps have been a recurring issue for Murray since Newport, Rhode Island, which was the first tournament he played after his disappointing second-round loss to John Isner at Wimbledon.
He has played 18 singles matches in that period, and when he ran through them in his head on Monday night, he found that he had experienced cramps in at least half of them. When your own body is rebelling against you, it becomes virtually impossible to compete.
"It's a really important off-season for me," said Murray, "because the physical side is nowhere near where it needs to be. I mean, like, my movement around the court is reasonable, not too bad. But if I'm not able to last, any ambitions that I have for having a good run at a slam are done. So, unless I get on top of that, and get myself in great shape, then yeah, I'm gonna end up disappointed."
Murray's decline was at least appreciated by the French crowd, who cheered Simon lustily in what is expected to be his final professional tournament. Afterwards, Simon told reporters that "I felt it was harder for him. Little by little, I could take my chance. In the end, he couldn't push on the first and second serves. In the past, he could play eight hours. The difference was more physical than tactical."
Will cramps be the end of muscleman Murray?
When Murray told reporters on Monday night that he hadn't been training hard enough, we looked at each other and then asked him to repeat himself - just for safety. We simply couldn't believe what we were hearing.
Murray's physicality was once described as "monstrous" by long-time rival Richard Gasquet. Admittedly, long-time fans still remember the gangling young foal who was crippled by cramp in his first high-profile match - the 2005 Wimbledon clash with David Nalbandian. But he has since indulged in all sorts of masochistic practices to improve his conditioning. In 2013, he even invited a bunch of hacks out to Miami to experience his regime: repeated 400m dashes along the beach, Bikram yoga in heated 40-degree studios, and endless sessions on the dreaded Versaclimber (a torturous device that simulates climbing a rope ladder, on and on, until you turn the awful thing off).
The process left us in pieces, but it had already been so successful in its stated aims that - after wiping out a two-set deficit against Gasquet on Centre Court in 2008 - Murray famously showed off his bulging bicep to the photographers' pit.
Now, however, his career has come full circle. On Monday night, as Murray slumped on a bench in the player lounge, he wasn't interested in talking about forehands and backhands. Instead he described the debilitating cramps that had just cost him the match against Gilles Simon, another long-serving Frenchman.
Unlike the Nalbandian encounter, this was hardly an epic. To his alarm, Murray had begun experiencing the cramps as early as 2-2 in the second set. "Yes, there were a lot of long points and everything," he said, "but having that happen after a set and a half on an indoor court where it's not particularly hot is really not acceptable."
Looking utterly crestfallen, Murray went on to admit that he had only put in a couple of strength and conditioning sessions in the gym since the US Open in early September. The fault, he insisted, was all his own, and nothing to do with his team or his fitness trainer Matt Little. When it came to his endurance training, he had simply dropped the ball.
Lacklustre effort at odds with quest to conquer cramps
You can see why the message came as a surprise. Apart from being furiously committed, Murray is usually fiendishly organised. When these cramping issues first surfaced four months ago, in the heat of the American summer, he spoke to his team and stepped up his hydration levels - which he usually optimises through the use of colour-coded bottles containing different levels of salts and minerals.
The process seemed to work when he moved into the third round of the US Open with no reported niggles. But it has resurfaced in recent weeks. "I'm not saying I'm going to win all of those matches," he said, after reeling off nine or ten different incidents of cramping since the summer. "There's no guarantee. But I'm gonna put myself in a much better position."
So how have we got here? Well, Murray is clearly limited to some degree in what he can do in the gym, because of the metal hip that he had installed during his "resurfacing" operation in early 2019. But if he can move around the court well enough to defeat the likes of world No5 Stefanos Tsitsipas, he should be able to sweat his way through a Versaclimber session without too much fuss.
One unfamiliar issue, which comes with his new status as a fringe player, has been a relative shortage of match time. "For the bulk of my career I would have played close to 80 matches a year," Murray said. "This year it would have been 40-something. I'm only averaging like one match a week. So the work that I do on the tennis court and on the practice court needs to be of a high enough intensity to make up for that. If I go a three-week period where I'm not playing many matches, I'll then probably need to do more on-court work as well."
Murray was at pains to emphasise that the cramps are nothing to do with his hip. "I need to be a bit more careful with some of the training that I do," he said. "But I can certainly do more, and push myself harder, than what I have done recently. What I'm trying to do is extremely hard. I need to do exceptional things to still compete. And yeah, if I'm being completely honest, I don't think the last four or five months that that's necessarily been happening."
One imagines that Murray's coach Ivan Lendl - himself an uncompromising trainer in his own playing days - would like to have his own say on this subject. But Lendl is a remote presence for most of the season, offering advice over the phone from his home in Florida. As a result, the success or failure of Murray's upcoming off-season training block - which is to include three-and-a-half weeks' training in Boca Raton with Lendl - will do much to shape his fortunes for the remaining portion of his career.
His tennis this year has improved significantly, carrying him from a ranking of No134 on Jan 1 to No48 now. If he were able to sort out his endurance as well, then he would become a real threat - particularly at middle-ranking tournaments such as ATP 250s and 500s. But if Murray continues to suffer from cramps, then this proud standard-bearer for British tennis may soon be forced to admit that his race is effectively run.