JOSE MOURINHO: Many had believed it was all but a done deal that the Real Madrid boss would return to Chelsea at the end of the season. But the Portuguese, while clearly hinting he is keen to manage in England once again, has never explicitly mentioned his old club. Despite a lukewarm endorsement from United legend Sir Bobby Charlton, Mourinho is the one man guaranteed not to be overwhelmed by taking on the challenge of following Ferguson.
DAVID MOYES: A persistent contender, who shares Ferguson's Scottish working-class roots. Moyes has plenty of admirers at Old Trafford due to the work he has done at Everton and his preference for the passing style United favour. Speculation has been intense of late that he is in his last season at Goodison Park, but has no real experience at the very highest level.
OLE GUNNAR SOLSKJAER: A host of former United players have been linked with the job in the past yet all have fallen by the wayside. The latest is Solskjaer, who has made a successful start to his managerial career at Molde. He lacks experience, though, and will benefit from Ferguson remaining at the club as a director.
JURGEN KLOPP: The Borussia Dortmund boss has made a big impression during his club's impressive run to the Champions League final. With a style of football that seems tailor-made for the English football and an at-times eccentric manner in his post-match interviews, he would be an intriguing addition to the Premier League.
LAURENT BLANC: Blanc had a brief stint with the Red Devils at the end of his career, so knows the club well. Caught the eye as manager of Bordeaux, where he won the French league title, then stabilised a France team that collapsed into chaos at the last World Cup before stepping down following their quarter-final loss to Spain at Euro 2012.