I don't think Carra is underrated to be honest, I think the only reason he seems to miss out at International level is because he is a victim of his own adaptability. Just because he CAN play right back doesnt mean he SHOULD play there. Gerrard is the same for England, just because he CAN play right mid and Lampard Cant, stevie gets shoved out there.
I think Rio Ferdinand is MASSIVELY overrated.
Pains me to say it but I think Carvalho is underrated, he doesnt get the attention because of the "Amazing" John Terry.
Scott Parker is underrated, his work rate and determination is unbelievable, I used to live up there (at uni) and the Toon Army were gutted when he left.