Sir Alex Ferguson has revealed his major reasons for not going after David Silva while he was manager at Manchester United.

The Red Devils were monitoring the Spanish playmaker during his days at Valencia before neighbours Manchester City signed him for £24million in the summer of 2010.

Ferguson told ESPN that Silva was certainly an interesting proposition but opted to stay away from the now two-time Premier League winner due to his apparent defensive frailties.

"We watched Silva a lot when he was at Valencia," Ferguson said.

"And the other player they had, the same type, years before it, played in that No. 10 role.

"My problem with that was you have to be very, very good to play in that position, because there's no defensive duties for them.

"So if you're wanting to be really successful, everyone has to do their turn, has to work, you know?

"So I had a difficulty with that. But, in the end, of course, there's the greats. You could say Lionel Messi was a No. 10 type, [Diego] Maradona, some fantastic players, and I don't dispute that.

"But at United we always found it difficult. The kind of No. 10 I used came from my experience as a footballer."