Roy Keane and Danny Baker have taken over from Eric Cantona and Chris Evans as enfants terribles of their particular professions

If Wednesday night turned the form book on its head, it certainly sent a few reputations tumbling too. Porto, billed as Europe's second best team (by Alex Ferguson no less) were apparently coming to Old Trafford to show Manchester United how it was done. United's only hope, we were told, was that Roy Keane would come steaming out of the tunnel breathing fire over the Portuguese men of war. Meanwhile, Danny Baker's controversial show on Radio Five Live later that evening was to provide a habitually thought-provoking end to the night's action.

Instead, Porto came, had a look, and obviously didn't fancy it. Meanwhile Keane and Baker sat on the sidelines, the former kicking his injured heels, the latter licking his wounds inflicted earlier in the day by the red card administered by his BBC employers (who claimed he'd "overstepped the mark once too often" with his comments about that referee and that incident). It was left to Ryan Giggs to cement his hitherto flimsy reputation with an immense performance. Bearing in mind that England are on course for an extra Uefa Cup place next season thanks to our current fair play standing in European competition, perhaps it was a good thing Keane sat this one out.

Ironically, Keane and Baker have taken over from Eric Cantona and Chris Evans as enfants terribles of their particular professions. Both are hugely talented yet capricious, prone to going in feet first without thinking. But while Baker licks his own wounds, Keane's misdemeanours often come at considerable cost to his own side. And while curbing Baker's caustic tongue would be akin to asking Graham Kelly to be upbeat, curb Keane's over-exuberance and you get, I believe, a truly great player rather than just a very good one.

He thinks differently, claiming last week that his occasional rushes of blood to the head are "all part of my game because I'm an Irishman" - which is like excusing every Scotsman from buying a round. Ian Wright is another regular miscreant who argues that if you take away his passion, the heart of his game is gone; like Sampson without the hair presumably.

But petulance, not passion, is surely the issue here. Wright and Keane are not hard men; they're simply aggressive players whose aggression undermines their ability. As the former Nottingham Forest defender Larry Lloyd once said: "Aggression is fine, provided it's channelled in the right direction. Keane thinks he's a hard man but he isn't in the same class as some of the real hard men. Ferguson's excuse is that Keane has a passion for the game. So did I, so did Tommy Smith and Graeme Souness - but we knew when to draw the line." Even Keane's former midfield partner Paul Ince claims that Steve Bruce and Mark Hughes are "the real hard men. They get battered and bruised every game but just get on with it". Indeed, Hughes has admitted that "the first lesson I learned at the top was to keep my mouth shut. Because the people doing all the talking are really the losers."

Ferguson defends Keane as "the most victimised player in the game", and there's no doubt that such players can be victims of their own reputations. At McDiarmid Park on New Year's Day, the St Johnstone midfielder Chic Charnley (now at Hibs) was introduced to me as "that player who always gets sent off". Charnley duly obliged, but his crimes were no worse than those being committed by his colleagues.

Yet they are invariably villains too, even if they are, Wright apart, conspicuous by their absence from the top 10 list of players carrying the most disciplinary points this season to date (a list headed by such "bruisers'' as Carlton Palmer, Billy McKinlay, Noel Whelan and Emile Heskey). While that might appear strange, given football's current card-happy climate, it does support the theory that referees are far more likely to give the usual suspects the benefit of the doubt than victimise them. The problem is that when they do over-step the mark they do so in style.

Proof that football's Samsons can play without their hair comes in the large bulk of Julian Dicks, a player who used to wear a T-shirt with the words "Hello. My name is Satan"; who keeps pot-bellied pigs and bulldogs in his front room; and who once admitted "I knew I was gonna hit him but I couldn't help myself".

Dicks was last sent of in September 1995. In the meantime he's curbed his misplaced aggression and matured into a left-back who can cross the ball as well as Andy Hinchcliffe, attack as well as Graeme Le Saux - with as much passion as Stuart Pearce. The cynics will say that Dicks is simply more adept at getting away with it, a view which any avid Dicks watcher will refute.

It's as if the player known as "Terminator" simply said to himself "I'll be back, and I'll still be hard, but I'll be fair too." So perhaps, instead of behaving like Danny Baker's favourite team, Millwall, and not caring that no one likes them, players like Keane and Wright should heed the best piece of advice meted out by Keane's former manager, Brian Clough, to Johnny Giles during his 44 days as Leeds manager. "God gave you intelligence, skill, agility and the best passing ability in the game. What God didn't give you was six studs to wrap around someone else's knee."