You can cross Chester Taylor's name off the list of free agents the Lions will look into signing.  He will be staying in the NFC North, but he is headed from Minnesota to Chicago, not Minnesota to Detroit.

Chester Taylor reaches agreement with Bears on a four-year, $12.5 million deal that includes $7 million gtd in year one.

The fact that Taylor was scheduled to visit the Bears first was a sign that he probably wasn't going to make it to Detroit.  Now the Lions will have to turn their focus to other running backs and hope to sign one.  If not, the running back position will have to be addressed via the draft for sure.  Right now it's not a necessity if the Lions manage to bring in a veteran running back, but if that doesn't happen it looks like they will have to draft one to add depth.

Side note: Chicago is on the verge of signing Julius Peppers as well.