Manchester United's success under Alex Ferguson was down to the former manager's intense demands of his "animal" players, Rio Ferdinand revealed.
Ferguson stepped down in 2013 after 26 years in charge and a remarkable 38 trophies.
The Scot's silverware haul included winning the Premier League 13 times and two Champions Leagues, with Ferdinand part of six of those title-winning teams at Old Trafford.
United have struggled since Ferguson's departure two years ago and former centre-back Ferdinand thinks the manager's recruitment of certain players was the key to success.
"Ferguson got rid of players who didn't buy into the Man United way, for one, or weren't capable of being intense every day," Ferdinand told ESPN FC.
"That's why you don't remain at a place like Man United. If you're not an animal who can go in there and be intense every day and demand from yourself and others to improve, you won't stay long... and good riddance."
Ferdinand, 37, added: "It [attitude] comes from the manager, I think, and the players identify that and then go and start playing that out on a regular basis, but I think obviously you need the manager to set the tone, and then the experience being able to deal with it.
"I came in to a squad [in 2002] experienced at winning. For example, when I came in, I never knew how to win. I was looking around like a sponge and I had Roy Keane, [Ryan] Giggsy, [Paul] Scholesie in that dressing room.
"And if there's a point in the season where I thought, 'Oh, gotta win this one, is it a nervous time, or are you meant to be remain chilled, or what?' You're looking at these lads, and they're preparing the same every game; they're just focused every game, every day in training.
"Focused. That's the difference, having people like that who understand it and know it.
"And, what happens, I've been there. I was the one who learned, and I was the one who showed the way, so I've done both sides. I know you're not born with it but there's got to be someone in that changing room who you go to because he looks like he's so comfortable with the situation, knows it. I'll follow that."
