Just how do you replace the irreplaceable?
That was the question facing Manchester United on Wednesday after Alex Ferguson announced his decision to retire as manager at the end of the season.
Everton manager David Moyes was installed by British bookmakers as the heavy favourite. The Scot has spent 11 years at Goodison Park and is a fiery, no-nonense coach in the Ferguson mould.
"What we are looking for is not someone to come in 10 months or three years, we want someone to come stay there and give stability"
Former United keeper Peter Schmeichel
Real Madrid coach Jose Mourinho, Borussia Dortmund coach Juergen Klopp and Ole Gunnar Solskjaer, a former United striker who has made an impressive start to his managerial at Norwegian side Molde, are also viewed as contenders.
The 50-year-old Moyes has shown loyalty and staying power with Everton - something that will go down well at United after Ferguson's long reign of more than a quarter century at Old Trafford.
With a tight budget, Everton are likely to finish sixth in the Premier League, ahead of Merseyside rival Liverpool for the second straight season.
"What we are looking for is not someone to come in 10 months or three years, we want someone to come stay there and give stability,'' former United goalkeeper Peter Schmeichel said Wednesday.
"When we talk about Moyes, he has been a decade at Everton and done a fantastic job on limited funds."
Moyes has craved the chance to manage an established European side and reportedly came close to taking over at Tottenham and Chelsea in recent seasons.
United has always appeared a natural fit. And he would have the blessing of Ferguson, who said Wednesday he will remain involved in the club as a director and ambassador and is sure to have a say in who succeeds him.
"Pep Guardiola, Jose Mourinho, David Moyes... there's a lot of successful managers out there,'' Ferguson said at the start of this year, answering a question about a worthy successor.
Being mentioned in same sentence as Guardiola and Mourinho can't help but boost Moyes' belief. United has never had a foreign coach, either.
"Pep Guardiola, Jose Mourinho, David Moyes... there's a lot of successful managers out there"
Mourinho has been heavily linked with a return to Chelsea this summer, but the United job is clearly one he would relish.
He has the gravitas and experience to step into Old Trafford and take over from the man he dubs 'The Boss.'
Mourinho has won a domestic league title at every club he has managed - Porto, Chelsea, Inter Milan and Madrid - and won the Champions League with Porto and Inter.
At the recent Champions League last-16 match between Madrid and United, Mourinho went out of his way to say all the right things in pre-and post-match news conferences, even saying the 'best team lost' after Madrid sneaked through on aggregate after struggling in the second leg.
Mourinho knows the Premier League well from his three seasons at Chelsea from 2004-07. But he has yet to build an empire at any of his clubs - three years is the most he has spent at one team - and that may be looked down upon in United circles.
With Guardiola already committed to joining Bayern from next season, the candidates to replace Ferguson are few and far between.
Rafa Benitez's short-term contract is up at Chelsea at the end of the month but it would be hard to see him at Old Trafford after his run-ins with Ferguson during his time at Chelsea.
Klopp is highly rated and regularly linked with a move to the Premier League, but it may be too soon for him.