Here's the reason why we're in good shape...
For the most part, the Celtics play team defense. Aside from KG, there isn't one defender who isn't replaceable within the system.
On the other hand, what we can't have is Pierce play extended minutes during playoff games. That's when PP starts to get streak-y. With Green, as his primary backup, Pierce will get plenty of rest for most of the contests.
As for Ray Ray, he is a streak-y shooter, as we'd noticed during both the '08 and '10 playoffs. The problem is that he goes cold w/o notice. This is a re-occurring issue.
I suspect that Pierce, with limited minutes, will be firing on all cylinders and will win most games for us, if we're in the crunch. Thus, I'm not worried, since I don't expect to see him do back-to-back 40+ min games.