Captain Roy Keane shocked English soccer on Friday by leaving Manchester United in mid-season after more than 12 years at the former champions.
Midfielder Keane, 34, joined United in 1993 from Nottingham Forest for a then British record fee of 3.75 million pounds and has been the lynchpin of Britain's most famous club for a decade.
Keane helped United win the Premier League seven times as well as the league and FA Cup double in 1994, 1996 and 1999 when United also won the European Cup.
He was the on-field mirror image of United manager Alex Ferguson - tough, uncompromising and interested only in winning - and the Irishman's departure after 326 league games for United signals the end of the most successful era at Old Trafford.
Keane, who has not played since September 14 because of injury, recently criticised team mates for lack of effort in a club TV interview which was never shown, and earned a public rebuke from Ferguson.
On Friday, Ferguson said Keane has been a "fantastic" servant for the club.
"The best midfield player in the world of his generation, he is already one of the great figures in our club's illustrious history," Ferguson said.
"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."
MISSED FINAL
United achieved a treble in 1999, including the club's second European Cup, but, having been instrumental in leading them to the Champions League final in Barcelona, Keane missed the dramatic 2-1 victory over Bayern Munich through suspension.
In September, Keane said he was likely to leave at the end of the season when his United contract ran out. Media reports say United have been actively pursuing Bayern Munich playmaker Michael Ballack to take Keane's place.
"The agreement allows Roy to sign a long-term deal with another club to enable him to secure his playing career beyond what would have been the end of his contract at United in the summer," United said on Friday.
Media reports have linked Keane with Scotland's Celtic and he is widely seen as having the credentials to coach a top team. The Ireland national team manager's job is currently vacant.
United have not won a trophy for the past two seasons and struggled in the early stages of this season to keep pace with champions Chelsea in the Premier League. They are currently fourth in the league, 10 points behind leaders Chelsea.
Keane said: "It has been a great honour and privilege for me to play for Manchester United for over 12 years.
"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.
SAD DAY
"At all times, I have endeavoured to do my best for the management and the team. While 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. I send my best wishes for the future to the management, players, staff and supporters of the club."
Ireland's Keane bowed out of international football last month after 66 caps, two days after the country's World Cup hopes ended in a match the injured player could only watch.
Manchester United said they had offered Keane, one of the most controversial figures in English football, a testimonial in recognition of his time at Old Trafford.
United chief executive David Gill said: "Roy has been a towering figure at the club for over a decade. His dedication, talent and leadership have been qualities that have marked him out as one of the true greats."
Earlier on Friday, United announced that winger Cristiano Ronaldo had agreed a two-year contract extension that will keep him at Old Trafford until 2010.
The 20-year-old and has become a first-team regular in attack alongside Ruud van Nistelrooy and Wayne Rooney.