Ferguson has been forced to make key decisions in the past even with some of his favourite players. And he will have to make more this summer as he revealed last month he could bring in three new signings in the close season.
Some will inevitably make way and the United chief added: "I love the players that I've had and I've been very, very fortunate to have had great players who have come through my career with me.
"At Aberdeen there were the likes of Miller, McLeish, and Kennedy, who were players that were very loyal to me.
"At United I've had Giggs, the Nevilles, Scholes and Butt, who represent the spirit of the club. All of the players that I have had here have played a part in my success.
"So when I see something happening, as in the cases of Nicky Butt and Phil Neville, I have had to release them to other opportunities.
"It was getting to the stage that I was terrified of talking to them and telling them they weren't playing.
"It wasn't fair to them because they were good players and played a big part in the resurrection of United.
"When the time came for me to let them go, I knew I was cutting really important, loyal strings and I didn't enjoy it."