Having started his professional football career in France with Sochaux, Rennes and Lens, Diouf finalised a move to Premier League side Liverpool prior[5] to the 2002 FIFA World Cup for Senegal and went on to have a memorable tournament.

He has also played in England's top flight for Bolton Wanderers, Sunderland and Blackburn Rovers before a stint in the Scottish Premier League with Rangers.

In 2011, he joined Football League Championship side Doncaster Rovers but was released at the end of the 2011–12 season following the club's relegation.

During his nine-year international career, he scored 21 goals in 69 caps, and also garnered considerable notoriety for a series of controversial incidents.

His continued impressive performances in the World Cup for Senegal, where they reached the quarter-finals, led to much excitement prior to his arrival in England.

[7][8] Diouf was the striker that manager Gérard Houllier hoped would take the Premier League title from Arsenal, after Liverpool had finished in second place the previous season.

The game marked a watershed in his career when, in the 87th minute, he spat at a Celtic fan, causing crowd disturbances and Diouf to be interviewed by the police.

He received a two match ban and was fined two weeks wages with Liverpool making a donation of £60,000 to a Glasgow charity of Celtic's choice.

[9] At the end of the season-long loan — and after scoring a mere six goals in 80 appearances with only three in the league — Diouf left Liverpool signing permanently for Bolton in the summer of 2005.

On 15 September 2005, Diouf scored Bolton's first ever goal in a European competition against Lokomotiv Plovdiv in a UEFA Cup match at the Reebok Stadium.

Diouf confirmed in an interview with the BBC that he would be leaving Bolton at the end of the 2007–08 season and that his goal against Sunderland on 3 May marked his last appearance at the Reebok Stadium.

[18] Then-manager Roy Keane stated he was happy that Diouf had joined Sunderland saying: "El Hadji has always been the kind of player opposition teams and supporters hate.

[21] Diouf scored his first home goal for Rovers at Ewood Park in the club's 3–1 victory over Wolverhampton Wanderers on 12 September 2009.

[22] On 21 March 2010, Diouf scored the equalising goal against Chelsea in a 1–1 draw at Ewood Park which opened up the 2010 title race.

He started the next two Premier League games against Birmingham and Burnley; he then made his fortieth appearance for the club at Fratton Park playing against bottom-of-the-league side Portsmouth in a 0–0 draw on 3 April.

On 20 August 2011, Blackburn manager Steve Kean confirmed that Diouf was not in his first-team plans, and that he expected him to leave before the end of the 2011–12 transfer window.

[24] On the last day of the 2011 January transfer window, Diouf joined Scottish Premier League champions Rangers on loan until the end of the 2010–11 season.

[27] In March 2011 Diouf was part of the Rangers team that won the Scottish League Cup after a 2–1 win over rivals Celtic.

[48] Diouf scored his milestone 5th goal of the season with a penalty to help earn Leeds a 2–2 draw against Brighton on 2 November.

[54] In December 2013, it was revealed that Diouf had missed several Leeds fixtures and training sessions due to unspecified 'personal problems',[55] and in order to attend the funerals of former mentor and Senegal coach Bruno Metsu and former President of South Africa Nelson Mandela.

[58] In November 2014, Diouf signed a one-year contract with Malaysian side Sabah FA of the Malaysia Premier League, and was named team captain.

He was also part of the Senegal team who were the runners-up in the 2002 African Cup of Nations, but was one of the players who missed a penalty during the shootout in the final as they lost to Cameroon.

[64] In 2011 Diouf was banned for five years from playing for the Senegal national side, after reacting angrily to claims that he had failed to attend a disciplinary hearing.

[77] Bolton fined him two weeks' wages and the FA banned him for three games after he pleaded guilty to a charge of improper conduct.

[79] On 20 September 2009, Diouf was questioned by police after allegations that he had made a racial slur to a ball-boy during a match at Everton, telling him to "fuck off, white boy".

[80] Diouf defended his actions by saying that the ball-boy had thrown the ball to him "like a bone to a dog" and that Everton fans were racially abusing and throwing bananas at him.

[86] On 27 April 2013, Diouf was shown a controversial red card at Elland Road after making offensive gestures towards the Brighton away fans.

[88] On 2 March 2011, Diouf was one of three Rangers players sent off in the Scottish Cup 5th round replay after an altercation at the touchline with Neil Lennon and dissent to the referee at full-time.