His total tackle numbers have been incredibly consistent the past 4 seasons. I'm not sure exactly why his tackle numbers on a game-by-game basis tailed off last year, but maybe a Buc homer can help out with that.
I did notice that he made the majority of his PDs in the 2nd half of the season. That suggests a possible shift in his responsibilities, or a shift in how teams game planned TB as the year wore on (meaning, maybe something forced Barber into more coverage than run support). Again, just speculation on my part, and hopefully someone with more insight can shed some light.
Either way, I'd be inclined to ride him 'til the wheels fall off. I'm not yet convinced, just by his 2nd half '06 numbers, that they have, yet.