No you don't play for so long at Utd if you're rubbish, that's why he moved there 12 years ago for £30m, but that was 12 years ago. Ferdinand is now 35, slow, injury prone and no where near as good as he was. Just because Ferdinand was a top, top defender, doesn't mean he is now. I'd rather Senderos now, who is still in his prime, than Ferdinand now, who is completely past it.
Keane played for Utd for 12 years and was a top player, should we stick him in midfield instead of being assistant? Actually, that's not a bad shout...
At 35 years old - lets say he played 10 games this season and is able to transfer his knowledge of the game etc. onto Clark/Baker/Okore.
Would this really be a bad thing?