Substitute Giggs broke Sir Bobby Charlton's all-time appearance record with his 759th outing in a United shirt and hit the winning penalty in last night's dramatic shootout victory over Chelsea.
"Ryan Giggs is Manchester United," said Ferdinand. "He is phenomenal. The thing is he has come on as a substitute and made an impact. He could have scored but John Terry cleared his shot off the line.
"He is not thought of as highly as he should be in my opinion. When he has retired, people will appreciate him much more.
"It is a shame really because he has been a fantastic servant to United and to football.
"To play so many games for one club is unheard of really, especially in today's game."