KO, in my opinion, was drafted to play with Rondo.
(1). He can play outside, and has a quick release. If they leave him outside, and he can consistently hit 3s (needs to massively up his percentage from outside) and long 2s, he can pull PFs out of the lane, and create spacing for Rondo, whose best work is done either driving to the basket, or passing from the lane.
(2). Although he lacks the lateral quickness to be a great defender, Rondo's on ball defense mitigates that to some degree. To SOME degree.
The bottom line is that, if he can develop into the jump shooter we all thought he could be, he will have unique value to Boston, playing with Rondo.