I've been a Crochet fan, but I think it's fairly obvious that he's a reliever and needs to have the 99-102 mph fastball to be effective at the MLB level.
They should just accept that, let him loose and turn him into Josh Hader.
If they want him to be a starter, send him down and make him prove it in the minors. Starting his clock is proving to be a huge miscalculation if they truly want Crochet to start.