Maybe you doubted there is anything more poignant in all of sport than the sight of a great champion falling against the ropes? You should, then, have been in the Centre Court here yesterday for the fall of Roger Federer.
You should have measured the distance he dived, the speed with which he slipped from some ultimate competitive grace to the confusion of the profoundest defeat.
You should have seen the dwindling body language and failing technique of the man who some time ago was enshrined as the most brilliant tennis player of all time when his opponent Jo-Wilfried Tsonga suddenly realised he could be rather more than another ritual victim in Federer's extraordinary career.
The 26-year-old Frenchman, known as the Muhammad Ali of tennis not for his legendary deeds but a striking physical resemblance to the great fighter, won his most famous victory not because he sensed that the man who had won 16 Grand Slam titles was suddenly, at 29, cornered and vulnerable.
No, it was because he reached a decision that, at the highest level of sport, so often provokes the kind of upset represented by Tsonga's 3-6, 6-7, 6-4, 6-4, 6-4 quarter-final triumph stretched over three hours and eight minutes of relentlessly intensifying action.
Tsonga grasped that there was only one way to break the enormous odds that had built against him when Federer moved clinically into his two-set lead. He didn't have the statistics but he knew the reality that in Grand Slam action Federer never loses such a lead – not until yesterday.
His record in 178 major tournament matches was a stunning 100 per cent after creating such an advantage before Tsonga began to produce shots which spoke of a talented player who knew that he was doomed without a major infusion of nerve and adventure.
The result was tennis as taut and brilliant as a world heavyweight title fight of the highest quality. For a while it was another Federer masterclass, an exhibition of the game's most subtle arts. Then Tsonga broke the Swiss master at the start of the third – and the desperate lunges of a drowning man became a superb, explosive pursuit of a semi-final place. No longer could Federer pull the string as effortlessly as a master puppeteer. He could play the most calculated shot only to see it wither against the force of the Frenchman's desperate but also inspired game.
The Centre Court had plenty of reasons to believe that Federer would find a way to check his tailspin but the more he ransacked his memory for the best of his game the more it seemed that he had surrendered, fatally, the vital momentum. In the first two sets Federer again made something like nonsense of the fact that he was seeking his first win in six Grand Slam tournaments. His shots not so much hit the lines as caressed them; his backhand looked as close to perfection as he had ever wanted it and his service was clinical enough to put the big-hitting Tsonga continually on the back foot.
But this was before Tsonga moved into a dimension which has often promised before but rarely reached at the most vital moments of his career. The Frenchman's own service acquired a weight and an accuracy that stripped down Federer's self-belief and when it came to the fifth set there was an increasing sense that the great man's faith in himself was draining away.
In the royal box Jack Nicklaus, still the greatest golfer of all time with 18 major titles – against Tiger Woods' 14 – hunched forward in his seat, the most rapt expression on his face. Perhaps he knew precisely the pressure mounting on his fellow champion, the terrible sense that he could no longer inflict himself on any situation.
When the cruel verdict was in, when Tsonga danced triumphantly across the Centre Court and Federer forlornly packed his bag, the big question came with an almost indecent haste.
Federer was asked if it felt like the end of an era. No it didn't, not to him. It felt like the end of a great tennis match. "No, I don't feel that way," he said, "because I played too good. It wasn't a shocking second-round loss in straight sets, some stupid match I played. It was a great match I think, from both sides. I really think I played well and I also thought Jo played an amazing match, as good as I've seen him play for a long period of time.
"You have to respect that, you have to understand it. That's why I don't believe I have to look too far ahead. I just have to accept what he did – and not forget that I have played well."
Tsonga was asked if he had felt a strange, strong force of inspiration. "Yes, yes," he said, "there was a lot of it. I felt so good on the court. I was quick. I was just perfect today. All the time I was feeling as though I was in a dream, even at two sets down because I was in a quarter-final with Roger Federer. The stadium was full. It was 6-3, 6-7. I was not ridiculous. I was in my match.
"You don't think to yourself, 'Roger Federer never loses from this position.' You just say that you have to be consistent, keep at your serve – and that's it. Then it comes true. When you are at two sets to one you say, 'OK, I can win another set – and then you are in the fifth set and you feel you can do anything."
Federer insists that he can still pursue the highest goals; he points out that Tsonga, for all his excellence on the Centre Court, was having his day of days, taking huge cuts at the ball and seeing everything work as if in a dream.
It was no reason to believe that an era had ended, he insisted, but the more he said it the more you had to wonder that he may just have been trying to soften the impact of his fall. This, it was impossible not to suspect, was the kind of defeat that makes the greatest of champions wonder quite how much time is left.
Federer loss in numbers
0 The number of times before yesterday that Federer had lost a Grand Slam match after going two sets ahead.
1 Break points created by Roger Federer, who could not get near Jo-Wilfried Tsonga's serve.
4 Times Federer had beaten Tsonga in previous meetings. Tsonga had only beaten Federer once before.
6 Consecutive Grand Slam tournaments that Federer hasn't won, dating back to last year's French Open.
9 Years since the last time Federer won no Grand Slams in a season. He has only the US Open left in 2011.
9 Break points created by Tsonga. He converted three of them, one in each of the third, fourth and fifth sets.
18 Aces delivered by the big-serving Tsonga. Federer had 17.
27 Minutes it took for Federer to take the very one-sided first set, which he won 6-3.
63 Winners hit by Tsonga yesterday. Federer managed six fewer, with 57 winners of his own.
121 Average speed, in miles per hour, of Tsonga's first serve. Federer's average was 114 mph.
135 Tsonga's fastest serve, in miles per hour. Federer's best was down at 126mph.
178 Grand Slam matches in which Federer had gone two sets up without losing before today.