1) 'I'd waited long enough. I fucking hit him hard. Take that you ...'

After Keane suffered a season-ending knee injury while trying to trip up Alf Inge Haaland in September 1997, the Irishman stewed for three years before exacting his revenge in the Manchester derby. "I'd waited long enough. I fucking hit him hard. The ball was there (I think). Take that you cunt," he recalled in his autobiography in 2002. "And don't ever stand over me again sneering about fake injuries. And tell your pal [David] Wetherall there's some for him as well. I didn't wait for Mr Elleray to show the red card. I turned and walked to the dressing room."

2) 'I didn't rate you as a player, as a manager, or a person'

Keane temporarily quits international football after a monumental slanging match with Republic of Ireland boss Mick McCarthy, in front of his team-mates in Saipan. Keane had expressed his frustrations with the side's preparations for the 2002 World Cup to the Irish Times, telling them: "You've seen the training pitch and I'm not being a prima donna. Training pitch, travel arrangements, getting through the bloody airport when we were leaving, it's the combination of things. I would never say 'that's the reason or this is the reason', but enough is enough."

Roy Keane appeared to resolve his differences with Mick McCarthy while he was manager of Sunderland in 2006. Photograph: Carl Recine/Action Images

That interview led to a furious row, during which Keane told McCarthy. "Mick, you're a liar... you're a fucking wanker. I didn't rate you as a player, I don't rate you as a manager, and I don't rate you as a person. You're a fucking wanker and you can stick your World Cup up your arse. The only reason I have any dealings with you is that somehow you are the manager of my country! You can stick it up your bollocks."

Keane leaves Manchester United after attacking seven of his team-mates on the club's TV channel, MUTV. Keane's most stinging vitriol was reserved for Ferguson's record signing, Rio Ferdinand. "Just because you are paid £120,000-a-week and play well for 20 minutes against Tottenham, you think you are a superstar," Keane said. "The younger players have been let down by some of the more experienced players. They are just not leading. There is a shortage of characters in this team. It seems to be in this club that you have to play badly to be rewarded. Maybe that is what I should do when I come back. Play badly." Not surprisingly the video, originally scheduled as part of the Roy Keane Plays the Pundit slot on MUTV, was pulled at the insistence of manager Sir Alex Ferguson.

As Sunderland manager in 2008, Keane was livid with Dwight Yorke, after the Trinidad and Tobago legend decided to come out of international retirement, jeopardising his club commitments. "Dwight's a clown and he's on an ego trip; he's brought this on himself. He's retired from international football about five times." Keane reserved the same treatment for Jack Warner, then Fifa's vice-president and a special adviser to Trinidad and Tobago's FA. "I think Jack Warner must be small because he's got small-man syndrome," he said. "I told him he was a disgrace and that I would not employ him. The man is a clown. I told him what I thought of him and where he should go."

Keane later walked out on Sunderland on December of that year, with Yorke claiming to have sent his former United teammate a text to wish him well for the future, to which Keane reportedly responded: 'Go fuck yourself' and later said that he would "take on board comments from people I respect but Yorkie is someone I don't have any respect for."

5) 'At Old Trafford they have a few drinks and the prawn sandwiches'

Keane hits out at sections of United's support in the wake of what he felt was a dire atmosphere in the club's Champions League clash with Dynamo Kiev in 2000. "Sometimes you wonder, do they understand the game of football?" he splutters. "We're 1-0 up, then there are one or two stray passes and they're getting on players' backs. It's just not on. At the end of the day they need to get behind the team. Away from home our fans are fantastic, I'd call them the hardcore fans. But at home they have a few drinks and probably the prawn sandwiches, and they don't realise what's going on out on the pitch. I don't think some of the people who come to Old Trafford can spell 'football', never mind understand it."

Roy Keane was angry about the way that Jaap Stam left Manchester United. Photograph: David Davies/Action Images

6) 'I didn't ask you to wait, did I?'

Even as a teenager, Keane is not afraid to stand up to authority. Following a friendly against the United States in Boston in 1991, the Republic of Ireland team are allowed a night out. The next morning, with departure set for 7.30am, the team are kept waiting until 8am by Keane. A furious Jack Charlton says: "Nineteen years old, your first trip, do you have any idea how long we have been waiting?" Keane replies, without a hint of fear: "I didn't ask you to wait, did I?"

Keane again criticised his country following a controversial loss to France in the 2010 World Cup play-off, in which Thierry Henry blatantly handballed in the build up to France's extra-time winner. Instead of joining the Irish FA's calls for a replay or sympathising with the team over the decision, Keane did the opposite: "Mentally, not strong enough. They can complain all they want but it's not going to change. France are going to the World Cup and they need to get over it.

'They want the sympathy. It's the usual carry on. It's boring – they would bore you to death they would. The same old Ireland – the world's against us – and because it was a handball it's a great excuse.'

8) 'Players are just expensive pieces of meat'

It's 2002, and Jaap Stam's £16.5m departure to Lazio finds Roy unhappy. Again. "His transfer to Lazio illustrates how little power footballers have in the game. Contracts mean nothing," he fumes. "He has discovered that, to football clubs, players are just expensive pieces of meat. The harsh realities remain and when a club decide they want to sell there is little you can do once the wheels are in motion."

Around all his bold statements, Keane has also been something of a soothsayer, and was one of the first to attack Joe Hart, even prior to England's No1 making a mistake during their 1-1 draw with Poland in October last year. Keane had told ITV: "There's a fine line between confident and cocky and I think he's been a little bit too cocky this year. He just relaxes a little bit and takes his eye off the ball … and he needs a bit more competition around him." Now that Joe Hart does have competition, was Keane's criticism justified?

This was not the only correct prophecy from Keane. Just prior to United's make-or-break Premiership showdown with Arsenal in 2002, Keane questions the desire of some of his team-mates and warns - correctly as it turns out - the Red Devils could end the season without a trophy. "There are a lot of cover-ups sometimes and players need to stand up and be counted," he admits. "I'm not sure that happens a lot at this club. That's the least we should do. We're not asking for miracles. When players don't do what they're supposed to do, it's bloody frustrating. We're going to find it hard to win the league and if we end up with no trophies there's something wrong."

Following Manchester United's Champions League elimination to Basel in 2011, Keane bemoaned the performance of United's youngsters: "You've had [Phil] Jones, [Chris] Smalling, [Ashley] Young coming in, everybody building them up, but they've got a lot to do. It's a reality check for some. I'd be getting hold of some of those lads, saying, 'You'd better buck up your ideas'." When a reporter asked about Keane's comments, Sir Alex Ferguson retorted "I don't know why you are bringing this up from a television critic."

In October, Keane accused Ferguson of not knowing the meaning of loyalty after the former Manchester United manager criticised him and other former players at Old Trafford in his new book. "I think I do remember having a conversation with the manager when I was at the club about loyalty. In my opinion I don't think he knows the meaning of the word.

"I find very, very strange to constantly criticise other players at the club who brought him a lot of success."