(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.
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Rio Ferdinand launches staunch defense of Alex Ferguson
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Former Manchester United boss is regarded as one of the best managers in world football
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United have struggled since the Scot left in 2013
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Louis van Gaal charged with restoring club's fortunes
Ferdinand, who won six league titles with @placeholder, says the new manager needs time to ensure his new signings gel and come together.