Comcast Sports Net New England is reporting that Boston Celtics Captain Paul Pierce has a knee problem that will prohibit him from playing in the upcoming four-game road trip. CSNNE says the injury could sideline Pierce for as many as two weeks. It is now clear that the Celtics recalled Bill Walker earlier on Wednesday in response to Pierce's injury. The Celtics' Captain scored 16 points in the fourth quarter of Tuesday night's game against the Indiana Pacers, including seven straight to put the Boston Celtics ahead for good in a 103-94 victory. Visit the Green Street blog for more on this story as it develops.