The Tampa Bay Buccaneers are placing Kenny Bell on injured reserve, according to Jason Cole. Bell injured his hamstring which caused him to miss the past two preseason games, though he was pushing to play in the fourth game. That apparently escalated rather quickly to injured reserve -- though this may just be the Bucs gaming the system and giving him a redshirt season. Which, incidentally, would not sit very well with the NFLPA.
With Bell off the roster, undrafted rookie Adam Humphries is almost certain to make the roster, while it opens the door for similarly undrafted Rannell Hall to make the roster as well as the Bucs cut their roster down to 53 players. Both Hall and Humphries were impressive in preseason and bring some value as special team returners.
It's possible the Bucs give Bell the designation for return, which would allow him to come back starting in week nine, but that seems somewhat unlikely given how much he has to develop to be a useful player this season.