(CNN) -- Rio Ferdinand was one of the world's top defenders -- now he's turned his hand to defending the reputation of his former manager Alex Ferguson.
The Scot, one of British football's most successful leaders, has been criticized in recent months following Manchester United's dramatic downturn in form since his departure.
Over two decades, Ferguson won 13 Premier League titles, two Champions League crowns, five FA Cups and four League Cups.
But after leading United to league glory in 2013, a title won by 11 points, Ferguson retired and appeared to take his magic touch with him.
Under David Moyes, United capitulated in alarming fashion, finishing seventh and failing to qualify for European competition.
However, some argued Ferguson had left his successor an aging squad, with the likes of Ferdinand, now 35, Nemanja Vidic, Patrice Evra -- two defenders who left Old Trafford in the summer transfer window -- Robin van Persie and Michael Carrick all in their fourth decade.
"I don't understand how people can say that," Ferdinand, who left Old Trafford at the end of last season, told CNN when asked whether Ferguson was responsible for United's failings.
"You've got some great players throughout the squad. You win the league by 11 points. You've got to be a top team to do that.
"So he goes and then it all falls apart. So that's his fault? How can people say that?"
Ferdinand, who won 81 caps for England, arrived from Leeds United in July 2002 for £30m, a world record for a defender at that time, went on to win six Premier League titles, the Champions League and two League Cups.
Now at Queens Park Rangers, Ferdinand was part of the United team which struggled badly last season under Moyes, the man who was handpicked by Ferguson to succeed him.
Moyes was relieved of his duties after just 10 months in charge and was replaced at the start of the 2014 season by Dutch coach Louis van Gaal.
Van Gaal has already made his mark by bringing in a number of high-profile players including Angel Di Maria from Real Madrid for a British transfer record fee of $98.7 million, Colombia striker Radamel Falcao on loan from Monaco and Dutch star Daley Blind.
Results have been mixed so far with United losing to the likes of Swansea and Leicester City, as well as being humiliated by third-tier side Milton Keynes Dons in the League Cup.
Two consecutive home wins over Queens Park Rangers and West Ham have lifted United to seventh in the Premier League table ahead of Sunday's clash with Everton at Old Trafford.
With Van Gaal struggling for defensive options and Ander Herrera, the midfielder, absent with a rib injury, United will once again by forced to field a changed line-up.
Ferdinand, who won six league titles with United, says the new manager needs time to ensure his new signings gel and come together.
"It's just about the new managers coming in and making that work together still," he added.
"Do they want wholesale changes? This manager seems like he wants to do that now. He's changing, making big changes. He's bought a lot of players in.
"So I don't think the buck stops with Alex Ferguson at all. I think you leave and you win a trophy.
"There's not many better ways to go out than that."