Walker, Giddens, Pruitt all have one more year experience. However that experience was mostly riding the pine because, even though the Celts were desperate for fill-ins from injuries, they couldn't be depended on. I don't see a high probability that any of them will be able to step in and contribute sufficiently. They all need more NBA experience and basketball IQ that can only be gained by playing, and I don't think there will be room for that on this years incarnation of the Celtics. They want to win it all, development isn't even on the Celtics wavelength this year.
But hey, that would be great if they did. I would still prefer them to sign someone or make a trade to fill out the roster.