I don't think teams in the C's position showcase players.
Walker is playing because he has been with the team for a while now after being injured, and has worked his way ahead of Giddens. If Walker was not back, Giddens would be playing against this horrid team. Doc has done this a few other times this year, when they are playing a terrible team, he has tried to give one of the young guys a few minutes at a point in the game where they can't mess it up too much.
Really, the only thing to take from this is that it looks like Giddens is no longer ahead on the depth chart.