£2.6m former Liverpool striker Diouf signs up for the bad-boy band at Sunderland

Sunderland supporters have spent months sniggering at the prospect of Joey Barton's return to rivals Newcastle.

But following the capture of Tottenham defender Pascal Chimbonda, a man who once handed in a transfer request straight after a Wigan end-of-season game and stormed off in a tantrum after being substituted during the Carling Cup Final, Keane has now snapped up controversial Senegal striker El-Hadji Diouf for £2.6million on a four-year contract.

In your face: Diouf (right) in typical form for Bolton, squaring up to Miguel Ferrer against Atletico Madrid in last season's UEFA Cup.

The 27-year-old former Liverpool striker was a regarded as a cult figure at Bolton and remained popular even when he announced his pending departure.

Although his pace and ability have never been doubted and were an asset to Sam Allardyce and Gary Megson, his volatile nature has never endeared him to opposition fans - as the poor unfortunates at Celtic, Portsmouth and Middlesbrough testified after they were literally given a mouthful by Diouf.

But as he announced his fifth summer signing before returning to Ireland for a game against Cobh Ramblers which his side won 4-0, Keane could not hide his delight that he had signed a player 'fans love to hate' to his squad.

Keane said: 'El-Hadji is a great signing and we're thrilled to get him in. He has bags of Premier League and international experience, which is exactly what we've been targeting this summer.

Diouf: unveiled by Sunderland

'He has always been the kind of player opposition teams and supporters love to hate, a thorn in the side, and that's why we're delighted to now have him.

'Our coach, Ricky Sbragia, has also worked very closely with him (at Bolton) and speaks extremely highly of him, so we're looking forward to working with El-Hadji.'

But even for Keane, the addition of such a volatile character as Diouf, and a man whose commitment is as questionable as Chimbonda's, represent significant risks.

When he was a player with Manchester United and Ireland, Keane was hardly renowned as a patient man with team-mates if their attitude was anything less than fully committed.

It is a streak which has yet to desert him as a manager. The reports from those within shouting distance of the away dressing room in Albufeira last week, following a very ordinary 1-1 draw with Vitoria de Setubal, suggest Keane has returned to pre-season in feisty mood.

He kept the players back for 40 minutes and very few escaped a tongue lashing. And no one, least of all the many players he has signed, is free from criticism, ridicule and his lethal assessment.

The bigger the fee and the reputation, the harder Keane is prepared to make them fall. As for players who knew how to wind up opposition fans, Keane was of course an expert and he may just thrive working with characters such as Chimbonda and Diouf who, on ability alone, will improve the standard of the Sunderland squad.

Keane's management style is unorthodox and yet refreshing. Some players like it, while others do not. If Chimbonda and Diouf are sulking in the stands and out of the Sunderland team in a couple of months, we'll know exactly where they stand with their new manager.