He's thinking about the crap he just had...
This is where it gets difficult, as you not only have to rely on the photographer to compose the shot, but also the model to be a great subject. I quite like the way this shot is composed but the model has no life, nothing to demand my attention, no intensity or engaging air around him at all. In fact he looks bored. He needs to relax, he needs to get into the mood a little more, and he needs to not think about holding the pose so much - that's when it becomes lifeless. Like I said, I don't have a problem with the composition though, even if it isn't the most interesting way to shoot it (just my opinion though)