Manchester United boss Sir Alex Ferguson admits winning a Premier League and Champions League Double is nigh impossible.

Ferguson was discussing the two competitions with Harvard Business School students:

"It's difficult to marry the two competitions in one season.

"We are in a country where tribalism is rife. There is strong competition between regions and top clubs, with Arsenal, Chelsea, and Tottenham based in London, two clubs here in Manchester, and Liverpool.

"That puts tremendous pressure on you to win your league. But the European Cup is the biggest trophy.

The biggest jug? The Champions League is massive, but...

"Last season, when we went out in the group phase, I made a mistake. I was playing a lot of the young players.

"Although that had worked in the past we got careless in our games.

"It was a shock, because it was only the third time I've not qualified for the knockout stage. I decided I wouldn't be taking the risks I took in Europe last year."