Ferdinand believes Giggs can eclipse Teddy Sheringham, Gordon Strachan and Kevin Phillips by stretching his playing career to span a quarter of century.
"I reckon he's got another two years left in him - it's a joke!" said Ferdinand.
"I'm 35 now and to see what he's doing now at 40 years old, I can't even understand it, the way I feel at times.
"It is phenomenal how he's kept himself in such good shape. He must have been very lucky with his genes."
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