It's not a practice issue and his arm is not what it was 5 years ago, to believe that is to be in total denial.
There are multiple examples of him underthrowing Ginn but look no further than his early INT against the Eagles in the playoffs. He has a clean pocket, has time to step into the throw and still throws it about 2 yards short...4-5 years ago that is a sure TD....
He is still more than good enough to lead us to another championship, but you better believe teams are aware that his arm strength is declining....I have faith SP can compensate for that with his brilliant play calling...just hoping the oline holds up better than last year....