I don't know what you have against Carroll, but numbers don't lie : QBs, with 1st round potential, that are leaving for the NFL early have not worked out as good as seniors. He just said the obvious. Might not be a ringing endorsement for Sanchez, but Carroll was on vacation in Hawaii and cut short his vacations to be by Sanchez's side when he declared for the NFL Draft...what more do you want from the guy ?
Also, with the Patriots team he inherited in 1997 he did about the same, statistics and record wise, than Parcells before him. Look at the stats on profootballreferences.com. He had no control over personnel decision, therefore you can't blame him if the team went bad...he remained the same coach from 1997 thru 1999. And again, if Belichick had to build the team from scratch in 2000, it's certainly not because Grier had left the Pats in a good situation...
Grier was also in charge for the 200 draft. Sure, Belichick and Pioli participated, but it's Grier who had done all the work in order to be ready for that draft since Belichick and Pioli had been in place for less than 3 months at the time. And, strangely enough, our first pick in the 2nd round was a bust. Grier was fired a couple of weeks after that draft, which should give a good idea of what Belichick and Pioli felt about him.
Say what you want about the Martin deal, but no, it wasn't the right way to deal with your best player. It's your best player, you don't wait for other team to dictate his value !!! I wouldn't say that for a guy you can easily replace, a position on which who have starting caliber backups, but in 1997 the backups to Martin were Derick Cullors and Sedrick Shaw (another superb Grier draft pick, 3rd round, by the way). If you remember what REALLY happened, the Pats just had signed up Lane and Rucci and did not have a lot of cap room...with Martin left to sign. The Jets, smelling blood, proposed a deal that the Pats could not match. It's BAD MANAGEMENT !!! And it is certainly not Carroll's fault !
Finally, about the comments on Cassel, I don't get what your point is : he was asked 5 years after the fact why he started Leinhart over Cassel. Carroll might not the the best coach ever, but he had to see something more in Leinhart than in Cassel in order to start. He just explained the reason why...it has nothing to do with his current players or installing doubts. And if Sanchez has doubts about his ability in the NFL following Carroll's comments, what kind of QB will he become after throwing 5 picks in a game ?? Professional athletes have to be stronger mentally than that...