I've been harping on this (his shooting) for weeks here at Celticsblog w/ few people agreeing with me... Glen has a role, and its a valuable role. Unfortunately he doesn't realize it.
People here, and even Hubie Brown during the 1st quarter, say that Glen is "a good shooter". Some even say he's "great". The fact is he's statistically the WORST JUMP SHOOTER ON THE TEAM (around 35%). Even Rondo is over 40% in jumpers.
His role is to body guys up on defense (which he did early on, and did well), set picks, rebound (which he sporadically boxes out on), pass the ball (when he does it results in good looks for other players), be a healthy big (I give him props for his reliability), and finish around the rim when he's dished to (which he's improved upon this year, and is quite good at).
He's not playing to his strength. But what bothers me even more is that on offense he's anti-unbuntu, he doesn't know his limitations, he's shooting when he's surrounded by 4 all-stars, and Doc & Co don't have the cajones to call him out on it.