Not sure what TT is trying to argue. DiPietro was a great young goalie, the kind who could turn away 40 shots a night and make spectacularly athletic saves. If he was healthy, he would have been worth every penny of his deal and he would be a steal at this point in his career. The lesson is that long term deals, even when the guy would still be young enough to play at the end of it, are bad ideas for the reasons that bit the Isles.
It has nothing to do with whether he was good enough to warrant that annual salary, because he was. He's now a cautionary tale of why 15 year deals, even for a young star, are stupid.