Shump seemed like the real deal this last season, but the guy automatically becomes a complete unknown with an injury as severe as an ACL tear that close to the start of the next season. If a guy who would be available in January at the earliest and might not be at full go for the entire season (or possibly ever), can get you a guy who will help you opening day, then you have to do it with a team like the Knicks.
I know the fear is that Shump is going to end up being an all-star caliber player in the future, but it ain't happening in the next calendar year because of the injury. We're the Knicks, we haven't had one of our own draft picks turn into a multiple time all-star since Patrick Ewing (unless I'm mistaken). We buy other people's stars, not grow them ourselves.