Here's part of the take on this from John Karalis at BSJ, who is IMHO the best Celtics beat writer out there now:
By the end of the last season, Boston’s offense ran through a healthy Williams, who displayed a natural passing ability that made him dangerous with the ball in his hands in the high post. It quickly became evident that the ball-movement, read-and-react style Stevens wanted was best achieved through Williams and his ability to make quick decisions and find cutters.
Add to that his freakish ability to sky for lobs, and Williams had proven himself to be a very valuable part of the team. The pressure he puts on the rim on pick-and-rolls has the ability to suck in all five defenders, opening up space for everyone to operate.
However, his biggest strides came on the other end of the floor. Where he once relied on those physical gifts to block shots out of seemingly nowhere, he has since improved his positioning and footwork to better prevent shots from even being taken. Slowly, he began protecting the rim with his presence rather than his jumping ability. And while he will still come out of nowhere to alter shots, his ability to slide laterally rather than turn his hips and run after attackers is what serves him best defensively.
...It’s hard to imagine that Stevens, who has had intimate knowledge of the type and severity of Williams’ injuries, would commit to five full seasons of him at the center spot if he was overly concerned about them (injuries going forward).
