We will never see one man dominate like Sir Alex Ferguson did, again

There has never been, nor can I imagine there will ever be, a harder job in football than to be the successor to Sir Alex Ferguson. The very best of luck to the man entrusted with perpetuating the era of dominance Ferguson has masterminded at Old Trafford. You are going to need it. It cannot be done and we will never see one manager dominate English football in the same way. Every other manager in England is rubbing his hands today, or at least they should be. The most formidable foe and intimidating obstacle to Premier League success will not be there any longer. The most powerful, inspirational manager of his generation standing aside gives everyone else far more chance than they have ever had.

There are managers who are described as irreplaceable, and then there is Ferguson who is at an altogether higher level entirely.

Ferguson's genius has been to weld the traditional values of the managerial titans - following the line of the greatest Scots, Matt Busby, Bill Shankly and Jock Stein - with the modern coaching techniques and psychological skills of any young pretender trying to catch him.

He not only possesses the 'old school' qualities of those coaching icons, he has moved with the times to become the archetypal manager for every generation. Today's game is a far cry from when he took over, given the financial rewards of players and the interference of agents. Ferguson has been able to ensure the first priority of everyone under his command is to win. That in itself, in an era of so many distractions for wealthy young footballers, is a triumph.

I've never seen any team of his that did not possess that unshakeable will to be successful, mirroring his personality on the pitch. You know when you are watching a Ferguson side, regardless of the Manchester United shirt.

We have seen it time and again over the years, United sides turning losing positions into crucial draws or victories in the last 10 minutes of games or in injury time. Some put that down to luck, but there has always been far more to it. Ferguson's capacity to make each of his players believe no position is irretrievable is a particular trait few others have been able to match to the same extent.

The general rule of football is the players win titles, the manager simply guiding what tends to be the most equipped squad to success. It does not matter how shrewd the guy in the dugout, if you've an inferior group at your disposal it will catch up with you over 38 fixtures.

Sir Alex has changed my opinion of this in the last three years. I believe if he was the Manchester City manager, they would have won a hat-trick of league titles. He has been the difference this season just as much as Robin van Persie's goals.

The timing of his departure is apt given he leaves United back in front of City, seeing off their challenge this season in the way he has all other rivals for the last two decades.

In some respects having initial success was the easy part. Sustaining it year after year is far more difficult. Ferguson managed to usurp Liverpool in the early 1990s, see off the greatest Arsenal team there has ever been and then faced the financial power of Chelsea and still won the Premier League title. The emergence of Manchester City was another fight he relished and overcame, bowing out having wrestled the title back from the wealthiest club in the world.

I recall watching United lose in the FA Cup at Anfield in 2006 and thinking they could be in some trouble for the next few years. Jose Mourinho had just won his second consecutive league title at Chelsea and there seemed to be signs of deterioration at Old Trafford. What happened next? United won three consecutive Premier League titles. I would not have believed they were capable, but that is Ferguson. Meticulously planning ahead to ensure there has never been any possibility of stagnation.

The debate inevitably rages as to whether Ferguson retires as the greatest there has ever been. The outgoing United manager is understandably ranked as the No?1 by his fans while others will point to Bob Paisley's haul of six titles in nine seasons, three European Cups and the Uefa Cup. Ferguson has never been able to dominate Europe as much as he has domestic affairs.

Having played under Bob, you would not expect a neutral conclusion from me and the truth is I do not believe it is possible to compare their success. Bob reigned for a shorter period in a different time and to accumulate so many titles in a compressed period was unprecedented. Equally, to win 13 titles since his first 20 years ago makes Fergie's success unparalleled in the history of the game.

Ferguson has also rebuilt his team more than any other manager, effortlessly easing star players out at the right time and maintaining his club's position at the top. That is another skill others have never been able to master.

To build one great side is enough to become a legend, but at least four? No one will match that.

His decision to remain at the club in some capacity will make it harder for whoever replaces him, knowing that shadow looms large. The comparisons with the last United great, Busby, are unavoidable.

Liverpool were fortunate to avoid the fate of United post-Busby because Paisley, Joe Fagan and Kenny Dalglish were promoted from within. There was no sense of upheaval or any feeling it would all fall apart. It is different when you appoint from outside the club, a manager arriving with his own ideas, seeking to establish himself in his own right.

A seamless transition is impossible now Ferguson has gone. He is the last of his breed and the Premier League will be a far less colourful, but possibly much more competitive, place in his absence.