Rivers has been doing this with rookies since he came to Boston. He sticks them in for a minute or two at a time in random situations and incrementally works them in. I don't see this as being much different. He's done the same thing with Pruitt this season. With pretty much every other rookie in previous seasons. I expect to see both Walker and O'Bryant on the court much more after the all star debacle.
I think if I had phrased my OP a little better, I would have asked whether Doc had planned on only playing Walker 2 minutes, or if he yanked him because of his on-court performance. A lot of people have already commented saying "he looked lost" out there. Perhaps Walker played poorly
and Doc had only planned to put him in for a few minutes.
People should probably remember that this is what Doc does, and has always done with his young guys. Even though it irks some fans, in fairness to Doc, the guy actually has a pretty good track record of developing young players, whether you attribute their success to him or not.