Trent Richardson's comeback attempt hits a big snag (Shutdown Corner)

Trent Richardson (AP)Baltimore Ravens running back Trent Richardson's attempt to revive his career was going to be a great story to track in the preseason, but now there is some concern that story might never begin to unfold.

The Baltimore Sun reported that Richardson likely needs arthroscopic surgery on a pre-existing knee injury, and it is unclear how long he'll be out. The Ravens' first training camp practice is July 28.

The timing of Richardson's knee issue couldn't be much worse. Richardson had already missed some OTA practice time with a hamstring problem. Richardson, who was out of football last season after being cut by the Oakland Raiders at the end of preseason, needs a very good…