Just three years ago Keane was being sounded out as a possible replacement for Sir Alex Ferguson at Manchester United, but now questions will be asked of the Irishman's managerial credentials, regardless of the level.
This has not always been the case. When Sunderland came calling in 2006 the Black Cats were in terminal decline. They had just been relegated from the Premier League after a record low points total and had lost their first four games of the Championship season, leaving them in dire straits under chairman and manager Niall Quinn.
Blown opportunity: Roy Keane must now choose his next path after leaving Ipswich
Quinn quickly decided he was not the man for the job, offered Keane his managerial chance. He had an immediate impact, with Sunderland winning their first game of the season 2-1 against West Brom with Keane watching from the stands. He was given the job the same day and wasted no time in using one resource the club did have - its financial clout.
He used his Manchester United links to bring in the likes of Dwight Yorke and Liam Miller, as well as four other players in a bid to steer the club away from a relegation battle.
Come the end of the season, Keane had achieved what was unthinkable only the previous August when he led his side to the title and promotion to the Premier League. Since the new year Sunderland lost just once and dropped points in only four games. Keane was on a roll.
The former Manchester United midfielder also passed the test in his first season in the top flight, leading the club to safety in 15th, three points away from the bottom three.
The trouble was Keane again threw money at the team pre-season and in the January transfer window, signing 16 players and not finding much success.
Kieran Richardson and Kenwyne Jones proved inspired buys but Greg Halford, Russell Anderton, Rada Prica and Michael Chopra added up to £10.5million flops and fans could be forgivenfor expecting more.
Heeven got involved in a club v country row when FIFA vice-president JackWarner blasted him over his decision to stop Yorke from playing for Trinidad & Tobago. Keane in his own outspoken way simply brandished Warner a clown: 'If he is vice-president of FIFA, then God help us.
Happier times: Keaneon his unveiling at Portman Road with Ipswich chief executive Simon Clegg
'Yorkie keeps making these cameo guest appearances for them, so maybe they have got some sort of deal going on themselves, I don't know. The man is a clown.'
Keane had hit his height at Wearside, after a run of five defeats in six games he walked out on Sunderland with the club in the relegation zone in December 2008. He had at least brought the club back to the Premier League but having spent £80m on 39 players did in reality what was expected at the very least.
After the dust had settled from his departure, Sir Bobby Robson pointed out the ex-Nottingham Forest midfielder's main flaw.
He said: 'I do not think he did his homework sufficiently when bringing in new players and it came back to bite him. You do not buy someone on the strength of a video or a scouting report, or seeing him once yourself. You look at that player carefully over a period of time, research his background, ask your friends in the game and then make your move.'
At the Stadium of Light he showed he was running a strict programme regarding discipline at the club. He infamously left out three players who were late for an away trip to Barnsley by simply letting the coach drive off on time, while he placed Miller on the transfer list for repeatedly being late.
On the decision Keane said: 'If you are driving to work, don't get in the car with Liam Miller because he has more car crashes than anyone I know. He is a talented boy and he has had his ups and downs. It's not a question about Liam the lad. I'm employed by Sunderland and I have to do what is right for Sunderland.'
After joining Ipswich in April 2009, Keane was hoping to match his previous feats and drag the club back into the Premier League for the first time since 2002.
However at Portman Road it started badly and soon got worse. In Keane's first full season with the Tractor Boys the club had its worse ever start, failing to win any of their opening 14 games. A club that was billed to challenge for promotion found itself in a season long scrap against relegation that ended in a comfortable albeit meek 15th place.
Despite spending £8m on players, Ipswich's fortunes declined rapidly under Keane, his only notable success during his time at the club being securing a Carling Cup semi-final tie against Arsenal which he will not even take charge of. Keane continued with his strict rules and only two months ago warned his own players of latching on to the new trend of wearing snoods during a game.
He commented: 'Don't get me started. I don't know how they do it. It's very strange. They can wear gloves in training, which I don't mind. One or two of our lads wore them last year in a cup game up at Blackpool. I made the point: "If you're going to wear gloves, you'd better play well. Because that's the first thing I'm going to throw back at you. You wear the tights, scarves, you'd better play well."'
Plenty of clubs were interested in giving Keane a start to his managerial career. A number of teams were willing to take a gamble after he left the Stadium of Light. But who is going to want him now?
First shot: Roy Keane was an instant success at Sunderland before losing his magic touch
There is no doubt Keane is still box office and should he get another job in management, it will be mainly based on the man rather than the manager. The clubs in question will argue that he did a reasonable job at Sunderland and that there is no reason why he cannot do it again.
This may be true but Keane had big financial help on Wearside and was not exactly dealing in peanuts at Ipswich. Not many clubs will trust him with a chequebook now.
His team's style on the pitch left much to be desired with free-flowing football not a prominent feature during his short career as a manager, while tactically his lack of experience has showed. Not even all those years under Fergie could help him.
Keane's options and selling points are becoming limited, should another job come calling he will have to improve greatly in the transfer market which has become his expensive achilles heel and he will do well to take the advice of the great late Sir Bobby.
The other key to his managerial future is his strict discipline in running a club. While there are many benefits to keeping players under tight rule, past players have spoken about not feeling at ease under Keane's management.
Ex-Sunderland defender Danny Collins said in the days after his departure from the Black Cats: 'We've been able to relax a bit more in training and in and around the training ground. In my personal opinion, when the gaffer was here, lads put a bit more into training, but if he wasn't it was a bit more relaxed out there.'
Keane's managerial career is not over but there may be only one last chance for him. His time at Ipswich showed that he has not learned from his mistakes at Sunderland and should he be offered another post he will have to change his approach. and maybe employ better scouts.
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