I think Mitch Rupert is sugar coating real concerns about Crawford. I think Crawford can still be a good starting MLB SS, although even that is not close to being a certainty. Of course, the skills he had are likely still inside him, as Mitch observes, and those skills caused evaluators to project reasonable odds that he would be an impact player at the major league level. Of course that positive an output is still possible, but IMHO the odds of it have fallen considerably since J. P. left A ball. The hope we can hold onto is that he has been playing hurt, which we know has been true for at least part of the past year, and is now healthy and finally once again doing what he can do.
The disquieting thing is that his offensive stats fell in going from CLW to Reading -- most hitters improve with that step up the line. His stats at Allentown are off more than 100 OPS points from what he did in Reading and it is now a full season of work. You don't erase that with a good 20 games. After poor offense over just about an entire year, he's going to have to put up at least another 20 good games, and realistically a good rest of the season, to erase the negatives from that bad year.
I've watched him play about 20 games between Reading and Allentown. I wanted to be impressed by his offensive skills, but I wasn't. I went back and checked his stats to see if it was just my jaundiced eye. It wasn't. His home/away splits tilt toward the away. HIs stats in Allentown this season are: .199 BA, .313 OBP, .622 OPS -- not at all good numbers, so what I remember seeing matches his stats.
Just by coincidence, I've seen him batting more against LHP than RHP. He's not good against LHP. His LHP/RHP splits are: OBP - .295/340; OPS - .573/.705. Whether you prefer OBP or OPS as your main metric, he is not hitting lefties well.
It naturally raises concerns when a hitter does progressively worse as he rises levels. There are fewer fat mistake pitches to cream. There are more LHP. You can't feast so much on not-very-talented pitchers filling out the A-league rosters.
I still think Crawford is our SS of the intermediate future. I still think he will be MLB average or a little plus. It is just very hard to see an impact player at this point in time.