I've found this quite bizzare so far. Drawing the NFL players throws your concept of perception completely off because they have helmets on, which makes their head a lot bigger, and also the shoulder pads elongate and heighten the shoulders. So, instead of the shoulders starting where the neck ends (generally speaking) they now start on a level with the ear.
If you drew a silhouette of one (I might do) they'd look like a distorted space alien, with a giant head and no neck.
I think this is good though because it means you have to look a lot more, rather than just jumping in and going 'oh yeah I know what a person looks like'. They're all different sizes too, for example you've got big butch built like a brickshithouse Ray Lewis, then you've got the much leaner Jerry Rice. The poses captured by the photographers are also really interesting and challenging, and nothing you could really get from a life model.
These are just doodles I did of Ray Lewis doing his thing. I looked at the paper for these. They don't seem to have worked well as when I didn't though. Well the one on the right didn't. His leg got messed up.
I seemed to have destroyed poor old Tom Landry here (right - hat)
This one I worked on afterward obviously.
Emmitt Smith (Left) looks to have a bit of a transformers head. I think my one of "the Fridge" turned out quite well (it's a separate picture of him on the top).
My first attempt, Adrian Peterson (Left) didn't go so well proportions wise. However I think I had a good stab at Broadway Joe Namath (right).