broken back? not one report mentions anything about a back injury. the isiah simmons "hit" you mention is of simmons pushing him out of bounds. and if you read the article about it...
His teammates signaled for the trainers to quickly tend to Atwell. After a period of medical attention, the receiver got up and jogged to the sideline to an ovation from the crowd.
further you may want to take a look around the nfl. in this draft alone roughly 10 5 9 speed recevivers were drafted. they are space players. its the way the nfl is going.
like just about every other draftee, atwell will put on some weight. i would expect the rams want atwell to play at 170 ala desean jackson.