Solskjaer announced his playing retirement last week and Ferguson said: "We felt he showed fantastic courage over the years with the problems he had with his knee.
"Ole gave us a bonus last year by giving us 11 goals. It was unbelievable.
"We didn't expect that.
"But his operations in March and at the beginning of the summer eventually got to him in a big way.
"He tried to train about 10 days ago and it didn't work out. He faced the reality that it had come to the end for him. It is not easy that.
"He could easily have jogged along and taken his money but it is not enough for Ole. He faced up to the situation."