you have 2 different arguments going- (mostly with yourself)
a) do i want him to remain a giant?- hell yes
b) is he worth top 10 money?- if he's top 10, he does.
if, by some chance the passer rating doesn't tell the whole story, then i'm ok with other criteria that make him top 10. if he has an average season and rides the defense to a championship a la dilfer, he should be paid accordingly.