I knew this thread was coming, and frankly, it's not fair.
First, there's no medical evidence to suggest that playing extended minutes contributed to KG's injury. Intuitively, it may make sense to draw the "more minutes = greater risk of injury" conclusion, but that's not proven in this instance.
Secondly -- and more importantly -- KG didn't average a lot of minutes this season. Here are his average minutes by month, from October until January: 31.0, 32.9, 33.4, 31.4. Only three times all season did KG play over 40 minutes. His minutes this season were the lowest since his rookie year, and were even lower than the 32.8 minutes he averaged last year. The year before we acquired KG, he averaged 39.8 minutes in Minnesota.
The last two seasons have been the only two seasons outside of his rookie year where KG has averaged less than 37.9 minutes per game. If anything, Doc has gone out of his way to make sure that KG *hasn't* played extended minutes. Again, blaming this injury on Doc is unfair.
(If Pierce was injured during the stretch where Doc refused to play Walker, there might be something to the argument. Here, it's without merit, in my opinion.)