Maybe you're right. But 3 years ago we were giving steady minutes to players like Gerald Green and Alan Ray. I don't think it's far-fetched to think that Walker could be playing on a crappy team. I just think that's different from the "Doc should play Walker and Giddens more" posts.
Three years ago, the Celtics had a ton of injuries and were tanking to move up to get more ping pong balls.
This past season, Giddens and Walker got about seven minutes per game each. As a rookie, Leon Powe got 11 mpg (although it was the tanking season). As a rookie, Glen Davis got 13 mpg (how much of that was garbage time?). You could say that the Celtics didn't have much other options for backup bigs, but then why didn't Walker and Giddens capitalize when Tony Allen's 18-19 mpg were lost to injury during the season?
Right now, I am willing to accept the coaching staff's apparent assessment that, through last season, Walker and Giddens (and Pruitt) were less capable of contributing than Tony Allen. (Folks, there is such a thing as a worse player than Tony Allen, believe it or not).
Come to think of it, if Tony Allen had never been a Celtic and were getting 30 mpg on some scrub team, there would probably be people on this board saying this his flashes of athleticism and ability to provide some good defense when he's not doing something stupid are sufficient promise for the Celtics to package some expiring contracts for him.