The rear delts usually get neglected, but this is a pretty easy fix and one you can do at home on a daily basis. The band pull-apart will bring your sad little finger-sized rear delts up to snuff quickly.
You don't need a heavy-duty resistance band because you're going to keep the reps high. Rock bottom rep range is 20, done for 4-5 sets daily.
There's nothing more frustrating than committing to a training program that doesn't pan out. This is equally true for an athlete who might work hard yet still falls short of his expectations and the strength coach whose biggest satisfaction comes from the great strides his athletes make.