Doug Plank, an American football coach, assesses most of his charges as "temperamental – that's 90 per cent temper and 10 per cent mental". Perhaps he is the man for Marat Safin, who has got through nearly as many coaches as he has smashed rackets.
For there can be no doubt which of the gentlemen contesting the first semi-final here today best conforms to Plank's template. Certainly not Roger Federer, the fleet, lissom seraph of the lawns, whose temperament flows like a cool stream over the rocky bed of his desire.
Safin, in contrast, lies open, dry and cracked, every fissure of his nature exposed to the bleaching heat of pressure. On the face of it, he would seem no more likely to make the final than Rafael Nadal's opponent, who might as well be served with a garnish of mint sauce. But Federer himself knows that there are three Grand Slam winners still in contention, not two, and to be prepared for absolutely anything from Safin.
As likely as not, he can expect the big man to prowl around the court in ursine desolation, muttering imprecations to himself in Russian, Spanish or English. Perhaps he will break a racket – he once broke 48 in a single year – or smash the ball clean over the stands, as he did during his quarter-final with Feliciano Lopez. When a Federer pass leaves him stranded, Safin will either spread his arms helplessly, Christ-like, or give a forsaken bellow.
But it is also possible, just possible, that Safin will thunder round the court with all the verve of Goran Ivanisevic in 2001, the year the smouldering Croat finally erupted. Perhaps he will conjure shots as far-fetched as the one that prompted him to drop his shorts for the delectation of Parisian women at Roland Garros in 2004. By all accounts, only the context was unusual that day. Safin has always known how to enjoy himself off the court: it is within its confines that his genius has too often seemed caged.
Before his arrival here, moreover, it seemed as though they had thrown away the key. Eight years ago, aged just 20, Safin beat Pete Sampras in straight sets in the final of the US Open. The world was his oyster. As if to prove the point, his post-match interview was interrupted by trolleys laden with caviar, lobsters and iced vodka.
He bought himself five cars. But he proved as furious as he was fast, and the wheels never stopped wobbling. He proved hopelessly inconsistent, bouncing giddily up and down the world rankings, changing coaches, strapping injuries.
Sometimes, he could peel away the distractions and find that the kernel of intuition remained intact. In 2005, he met today's opponent at the same stage of the Australian Open, won in five sets, and then had the temerity to beat Lleyton Hewitt in the final. But last autumn he was so disenchanted that he abandoned the tour in favour of Cho-Oyu, the sixth highest mountain on the planet.
The fact that he abandoned that project, after a trial ascent in the Himalayan foothills, might be considered instructive of a feckless nature. When he arrived here, after all, he had won consecutive games only twice all year. He was ranked 75, and the notion that he might pillage his way into a semi-final seemed preposterous. But he claims to have been working ferociously hard, even missing the chance to watch his sister, Dinara Safina, in the final of the French Open, instead persevering with practice. He also endured the indignity of coming here via a qualifying tournament in Hamburg.
Safin has always professed a suspicion of the surface, despite having the build and belligerence of many grass specialists. But in the second round he eviscerated the third seed, Novak Djokovic, and those big feet have boomed through the top half of the draw ever since. "I wouldn't have predicted it before the tournament," Federer admitted yesterday. "But once he's on a roll, he's quite unstoppable. He has beaten me on big occasions in the past, so I will not be underestimating him. I will have to be very careful."
Overall Federer has his measure, 8-2, and Safin offered a bleak formula for beating the champion: "You have to be Nadal, and run around like a rabbit, and hit winners from all over the place." But another, very different Russian player, Yevgeny Kafelnikov, long ago identified the fact that the odds, in any match, would always depend on Safin, and not his opponent. "Marat is so talented, he will be as good as he wants to be," he said.
And, just now, it seems that he wants to be great again. Ethnically, Safin is a Tatar, like Rudolf Nureyev. Tatars distinguish themselves from Russians as both more fiery, and more sensitive. The question is whether these attributes will encumber Safin, this time, or exalt him.
Life and times
Born: 27 January 1980, in Moscow, Russia
1997: Turned professional.
2000: Winner of US Open, beating Pete Sampras in straight sets in the final. Became world No 1 later that year for a nine-week spell.
2002: Davis Cup winner with Russia.
2003: Missed the majority of season due to injuries.
2005: Winner of the Australian Open beating Federer over five sets in the last four and Lleyton Hewitt in final.
2006: Davis Cup winner with Russia.
2008: Reaches Wimbledon semi-final for the first time in his career. His previous best was a quarter-final berth in 2001 where he lost to the eventual champion, Goran Ivanisevic.
Singles Titles: 15.
Runner-up: 11 times.