Diouf 's new spat with fan

A Cleveland police spokesman said: ' We are investigating a complaint made by this family into the alleged actions of a Bolton footballer at the Middlesbrough against Bolton game.'

Diouf first sprang to the attention of European football with an enchanting display for Senegal as holders France were humbled in the opening game of the 2002 World Cup.

But, since his exhilarating contribution to his country's success in Japan and Korea earned him a £10m move to Liverpool a little over two years ago, he has become too readily associated with the more sinister side of the game.

Bolton manager Allardyce may believe Diouf is merely in need of the same care and attention extended to many of the other waifs and strays he has turned into respectable footballers at the Reebok.

But the former's lone voice is becoming lost amid the din of derision starting to follow Diouf from one Premiership away ground to another.

Many believe him to be a cheat, too ready to throw himself to earth as soon as a defender arrives within sniffing - never mind tackling - distance. Others, meanwhile, believe he is worse than that - a loner with a mean streak, too selfish to put his team's needs ahead of his own.

Even Allardyce himself has warned Diouf about his behaviour this season, saying: 'He's getting people agitated and infuriated and he needs to control that side of his character because it will do us and him no good in the end.

'He's improving with every game, but he just needs a quiet word to curb the other side that might get him sent off. He also does go down a little too easily and, when he does get fouled, referees tend not to give free-kicks.'

On Saturday at Bolton, Diouf's apparent rehabilitation under Allardyce continued as he scored again. It is, however, events on Teesside a week earlier, that are casting doubt on his future.

Despite scoring twice on his Premiership debut, Diouf left Liverpool in the summer having scored just six times in 80 games. Former coach Gerard Houllier described the £10m he spent on him as 'my biggest mistake' while current Anfield boss Rafael Benitez does not want him back.

Diouf remains popular in Senegal but is currently on a last warning after breaking a curfew ahead of a World Cup qualifier with Liberia.