"Fletcher signing a new contract has probably been the relief of the season for us because there were a lot of clubs trying to buy him," Fergie told The Sun newspaper.
"He had just one year left on his deal and he wanted more football than he got last season.
"I said to him 'Look, you were brought up at this club, you've got to recognise we played you in all the big games last season until you got injured in February'.
"That injury kept him out for four or five weeks but he then came back and played in some more big ones, Chelsea away and Barcelona in the Champions League semi-final at home.
"Darren played in all the big games and I think that convinced him to stay.
"Now, with the injuries we've had, we're seeing he's such an important player for us. He's developing and improving his game and taking it to a new level."