In EVERY game there is a point at which the energy level of a given team may go down, that's why teams go on runs. The thing is you're not giving credit to the Knicks for one, changing how they defended Granger and more over picked up their Defensive effort. Nor are you giving them credit for playing better offensively. I think you need to look at the game again and watch the way Knick defenders got up into the Pacers on the perimeter. They got more tips and steals and overall just befuddled the Pacers with their defense.
Now I don't like the fact that the team fell behind by large digits yet again. I think tho that in almost every game they've had at least one qtr where their offense completely falls apart. It's those lulls that have really been at the heart of the losing. This team was never a great defensive team and so when they lose it's MOSTLY due to poor offense. When they play better O, they tend to pick up effort on D. It shouldn't be that way, but that's the true nature of offensive minded players.