The Senegalese player's talent has never been in doubt, but it has often been overshadowed by controversy
El-Hadji Diouf's battle with self-discipline continues
A dense fog hung over the city of Tunis. It was the day of the 2004 African Cup of Nations final, of eager anticipation for the hosts, and huge expectations for Senegal, who hoped that the finest collection of players in the history of their football would, for the first time, be crowned champions of their continent.
Alas, the hope vanished in a red mist, their superstar striker at the centre of it.
El-Hadji Diouf, his face screwed up in anger, became suddenly incensed, his intentions towards the referee, the UAE's Ali Bujsaim, so aggressive that his teammates struggled to restrain him.
Diouf's protests about Tunisia's match-winning goal would see him sent off, then sulk ostentatiously on the touchline, and be banned for two more matches for his country, the Senegal he had so often helped inspire. In that moment, a long decline for the Senegal team began.
It had been in the jersey of Senegal that Diouf first caught the attention of a wide, global audience. With his peroxide-blonde hair, he set out to draw attention to himself at the 2002 World Cup; with his pace and determination, he demonstrated he was no mere showman.
Senegal beat France, the champions, in a sensational opening game to the tournament, the 1-0 victory achieved when Diouf zipped past Frank LeBoeuf to provide the crucial cross.
By the time Senegal were busy knocking out Sweden in the knockout phase, Diouf had compiled quite a medley of memorable tricks, like his nutmegging of Olof Mellberg, the Swedish defender, or his role in the see-saw 3-3 draw with Uruguay, when his feigning earned Senegal a penalty.
There have been other dives since, and several more flashes of temper and incidents of slyness. But then, there was always a rough edge to the individual.
Diouf grew up in a poor quarter of Dakar, the Senegalese capital; there, he became involved in petty crime. In France, where he had realised the dream of so many West African teenagers, of a professional apprenticeship, he fell foul of the law when he was caught driving without a licence.
Once in England, where he has now lived and worked for eight-and-a-half years, he would rub many up the wrong way.
"El-Hadji Diouf is a liar," Gerard Houllier, the former Liverpool and now Aston Villa manager, once told me, listing various episodes when Houllier felt the player had been disloyal and told untruths.
Houllier still feels let down by a footballer whom he recruited for Liverpool just before the 2002 World Cup.The Frenchman had followed Diouf's impressive progress with Lens in Ligue 1, and as others observed Diouf's performances in South Korea and Japan, the signing looked like a fine piece of foresight.
But Diouf's time at Liverpool would be mixed. He scored fewer goals - only three in 54 Premier League matches for the Anfield club - than Houllier would have hoped for, though, in his defence, it has never been accurate to regard the player as an out-and-out centre-forward.
He is best attacking from wide or deep positions. At Liverpool, too, there would be controversies.
Diouf reacted horribly to being goaded by a Celtic fan behind the goal during a European tie against the Scottish club; he spat at the spectator.
At Bolton Wanderers, where Diouf moved after two seasons with Liverpool, he would find a more comfortable niche.
Diouf rediscovered the sort of regular goalscoring form of his days at Lens, and his effervescence and imagination on the wings excited the Reebok Stadium.
When Diouf moved to Sunderland after four seasons, Bolton fans were in the vast majority sad to see him go.
At Sunderland he would memorably be welcomed by the then manager Roy Keane as "player who opposition teams and supporters hate".
His stay there was brief - one year - before Sam Allardyce, his former coach at Bolton, brought him to Blackburn Rovers.
There, he has contributed match-winning performances, but, inevitably, there have also been scandals: an allegation that he swore at a ball-boy at Goodison Park; more trouble with driving offences and, earlier this month, the apparent taunting of an opponent, Queens Park Rangers' Jamie Mackie as Mackie, in pain and on the ground, suffered a broken leg in an FA Cup game against Blackburn.
"I have always needed a challenge in life," Diouf once said to me, "and I am a battler and in English football you need to have some fight."
He also remarked in the same interview: "You have to keep the rigour and discipline about what you do."
Diouf turned 30 last Friday; he is still battling, has become an enduring presence in the varied and demanding theatre of the Premier League, but the target of consistent self-discipline still seems like a work in progress.