Sir Alex Ferguson was forced to confront his greatest fear head-on last night when Roy Keane revealed he will quit Manchester United at the end of this season.
As Keane approached the final years of his illustrious career with United, Fergie admitted he faced an impossible task in replacing the player he considers the best he has ever worked with.
"I've looked all over for a replacement for Roy Keane but the simple truth is that there isn't one out there," said Fergie just a few weeks ago. "He's just irreplaceable."
For 12 years, Keane has been the embodiment of Fergie on the pitch, the player behind United's relentless success over the past decade. But the end of that glorious era is now in sight.
Of course, Fergie has seen this moment coming for the past few years, and has rationed Keane's appearances in an effort to prolong his career at United.
During that time, a succession of midfielders have walked through the Old Trafford doors, some of them burdened with the tag of being labelled as Keane's natural successor.
Juan Sebastian Veron, Eric Djemba-Djemba and Kleberson have all been and gone, none remotely close to matching Keane's extraordinary drive and remorseless influence at United.
Fergie talked of Steven Gerrard being the closest thing to Keane in his pomp, but conceded the bitter rivalry between United and
And a few weeks ago, Fergie revealed he was told of Patrick Vieira's availability in the summer but did not pursue the former Arsenal captain because he had turned down United before.
So the United boss has been forced to look within his own ranks for a possible successor to Keane, with Alan Smith emerging as the latest applicant to be tested in the midfield role.
But Smith is unlikely to make the position his long term and next summer, or perhaps in January, Fergie must buy a big-name central midfielder.
Few United fans would oppose the signing of Bayern Munich's powerful and influential midfield general Michael Ballack, who - like Keane - is out of contract next summer. At 28, Ballack is entering his prime and his knack of scoring vital goals, as well as his proven ability at every level, makes him an ideal choice. And with no indication that Ballack will agree a new deal with Bayern and so can talk to other clubs on January 1, Fergie must move fast.
Fergie and his scouts have also identified St Etienne's Didier Zokora as a potential target, with
Zokora, an
And while he looks at potential targets, Fergie is also certain to urge the United board to offer Keane a one-year extension.