STEVE McClaren last night claimed there would be "a queue" of managers wanting to sign Roy Keane - and the Middlesbrough boss will spend the next week deciding whether or not he should join it.

Keane parted company with Manchester United yesterday to end a 12-and-a-half-year association with the club and spark a flurry of speculation regarding his future.

The volatile midfielder, who was due to leave Old Trafford at the end of the season, has been at loggerheads with Sir Alex Ferguson since he controversially criticised a number of his team-mates in a video that was due to be aired on MUTV earlier this month.

The pair are understood to have rowed again yesterday morning about Ferguson's decision to strip Keane of the captaincy and, within hours, Manchester United were announcing that the Irishman had left by "mutual consent".

By mid-afternoon, Portsmouth had become the first club to declare an interest in signing him. They are unlikely to be the last. Despite turning 34 in August, the midfielder remains a formidable midfield presence able to command respect in any dressing room he enters.

McClaren knows all about Keane's qualities from his time as Ferguson's assistant and is adamant he has still has plenty to offer in the Premiership.

The Boro boss remains one of the Irishman's few footballing friends - the pair spent time together at United's Carrington base while England were training there last week - and is expecting a stampede of clubs desperate for his signature.

Boro's current transfer policy is only to sign players under the age of 28 but, with Ray Parlour injured and George Boateng currently stalling on a new deal, it would be no surprise to see McClaren bending the rules to offer Keane a short-term deal at the Riverside.

"My first reaction was shock," said the Boro boss. "It's the end of an era. What a player - one of the best players ever to have pulled on a Manchester United shirt.

"I'm delighted that I had the pleasure of working with him for three years in a period when, for me, he was the best midfield player in the world.

"He's still a very good player. You never lose your leadership or the aura he would bring to any football club.

"Whatever he does, he gives 110 per cent, so there's no question about motivation. He's always motivated so you'd have quite an asset there.

"I would think there will be a host of clubs interested in him. A lot of clubs would love to sign a player of his calibre.

"I'm sure there'll be a queue of clubs wanting him. Will we be in that queue? We shall have to see."

Keane's time at Old Trafford made him one of the game's most successful, but controversial figures.

He helped Manchester United win seven Premiership titles, four FA Cups and the Champions League, but also led the posse that hunted down referee Andy D'Urso - against Middlesbrough - assaulted Alf Inge Haaland and left the Republic of Ireland camp in disgrace ahead of the 2002 World Cup.

His legendary short fuse might have got him into a succession of scrapes during his United career but, according to McClaren, his combustible personality was integral to both his, and his club's, success.

"I think he's one of the last of that kind of generation," said the one-time United assistant. "You won't get many players like Roy Keane ever again.

"He's a leader on and off the field. He's a combative midfield player, but he can also play and influence a game.

"We always got on very well. I think we're similar people because we're both very ambitious. We do things for the good of the club.

"Whenever Roy exploded or said he wasn't happy with something, it was for the good of the football club.

"That's the character he is and the personality he's got. If something's wrong and he's not happy about it, he has to tell people. When it comes to diplomacy, there's a question mark."

Keane has previously spoken of his desire to end his career in Scotland with his beloved Celtic but, with Gordon Strachan having replaced Martin O'Neill in the summer, that may no longer be an option.

The likes of Wigan and Bolton are likely to be keen to keep him in the North-West, while oil-rich clubs in Qatar are already believed to be lining up a series of lucrative offers.

Keane could yet enter management with the Republic of Ireland but, while he ultimately sees his future in coaching, his playing days are unlikely to be finished yet.

"I can only go on what we've got here," said McClaren. "Gareth Southgate is 35, Colin Cooper was playing when he was 38 and is still playing for the reserves now.

"You get characters like that in the game. If you look at the example of other players, you'd say he's got a few years left in him yet."

Manchester United have granted Keane a testimonial despite his hasty exit from the club and Ferguson was quick to pay credit to the role he had played in more than a decade of success.

"Roy Keane has been a fantastic servant for Manchester United," he said. "The best midfield player in the world of his generation, he is already one of the great figures in our club's illustrious history.

"Roy has been central to the success of the club in the last 12-and-a-half years and everyone at Old Trafford wishes him well in the rest of his career and beyond."

Keane was similarly complimentary, praising the United fans and expressing his sadness at the day's events.

"It has been a great honour and privilege for me to play for Manchester United for over 12 years," he added. "During my time at the club I have been fortunate to play alongside some of the best players in the game and in front of the best supporters in the world.

"At all times I have endeavoured to do my best for the management and the team.

"Whilst it is a sad day for me to leave such a great club and manager, I believe that the time has now come for me to move on. After so many years, I will miss everyone at the club."