Man, it's like people didn't even watch the Celtics play last year.
The Celtics were a much better defensive and offensive team with Bradley in the starting five. Not because KG got better post-all star break, Bradley was just flat out better than Ray last year. And no, Ray didn't have bonespurs all year and even to start the year was a sieve on defense. Instead of Rondo having to guard the best guard and run the entire offense, Bradley was able to take some pressure off Rondo.
On top of that, Bradley isn't completely dependent on getting 3 consecutive screens and a perfect pass from Rondo to get a decent look. He can create his own shot and make offense even when the offense is being run through another player.
Bradley is just flat out better than Ray, healthy or not. On top of the fact Bradley is a young budding player, there is absolutely zero valid argument to be made for Ray starting over him.