By Dan Warren BBC Sport Online

Historically, British football fans have always reserved a special place in their hearts for the hard men of soccer.

For whatever reason, fans love their club to have its own "psycho", a no-nonsense tackler whose uncompromising challenges swiftly end the opposition's attacks.

Should Keane be punished?

Yet when does a hard man become a dirty player? It is a fine line, and one that Roy Keane may just have crossed.

Keane's admission in his autobiography that he deliberately set out to injure Alf Inge Haaland in the Manchester derby of 16 months ago could destroy what remains of his reputation.

Keane facing FA rap

True, many have already dismissed Keane as a thug, although he does still have an army of supporters.

Lovers of the physical side of the game in general, and Manchester United fans in particular, revere him as a hero.

Roy Keane famously clashed with referee Andy D'Urso

That he is a world-class player clearly helps.

But Keane is increasingly putting himself out on a limb as one outburst follows another.

His fiery nature attracted fierce criticism as he led a posse of Manchester United players in chasing referee Andy D'Urso after the official dared to award a penalty against Sir Alex Ferguson's side in September 1999.

Others were involved, but it was Keane, leading the pack, wide-eyed, with veins looking set to explode, who really caught the attention.

He has rarely been far from controversy since.

But he was perceived to be a more level-headed character, in charge of his anger, ahead of this summer's World Cup.

The ferocious row with Mick McCarthy which hastened his return trip from the Far East soon changed that view.

The truth about that row was shrouded in claim and counter-claim, and opinion in Ireland seemed split as to whether Keane was villain or victim.

But in Britain, many considered his outburst unreasonable and his behaviour childish.

And his subsequent revelation about that tackle on Haaland can only erode his reputation further.

Haaland has barely played since his injury

Most fans knew that Keane harboured a grudge from 1997 when Haaland, then of Leeds, allegedly accused him of play-acting as the Irishman suffered the cruciate ligament injury which was to keep him out of football for one year.

That his revenge tackle against Haaland was appalling was never in question.

Keane received an instant red card and three-match ban, although some suggested the suspension should have been longer.

But the revelation that the assault was as pre-meditated as it was sickening will win no fans.

Keane will still find some advocates.

Old-school football fans will point to the 1970s, where Ron 'Chopper' Harris and his hard-man peers dealt with skilful players by kicking them in the air.

They will claim today's stars are an over-cosseted bunch of fairies who deserve to have the wind put up them.

And United boss Ferguson will never speak ill of the captain who has been a key figure during United's years of success.

Yet most football fans like their psychos hard but fair.

And they will realise the sight of Keane intentionally slamming his studs into Haaland's knee has no place in the beautiful game.