"Shanks, Paisley, Stein and Cloughie and all those other great managers were marvellous but Sir Alex tops the lot.
"We had not really crossed swords until I took on the Newcastle job in 1999 and then it was one to one but our relationship was great.
"He has a man-management style which is successful with his players. He knows how to win, he understands losing and he has proved beyond doubt he is a fabulous football manager.
"He has got a great human side to him. He always has time for ex-managers and ex-players and anyone who rings him up.
"He can go on for a while yet as he can delegate. He has got great staff, great players and as long as he controls all of that, he can go on for as long as he wants.
"I wouldn't be surprised if Alex goes on after this season for another three to five years.
"Why should he retire? If he enjoys it and continues that success, I think he will last that long but at the end of the day it will be up to him."