i'd say shelton's 'racket head discipline' is ok...he just has a weird hooking motion to his forehand, doesn't catch it out front enough imo. actually zverev does something similar, which is why he doesn't have the best dtl forehand. goran did a similar thing for those who remember, kind of came around rather than out and through it. his backhand isn't bad either, but similarly doesn't extend through it like a nalbandian, safin, others...
all in all though his ground game is not bad, he's just not rock-solid consistent...but then again he's not alone there. honestly i'd love to see him improve his serve accuracy more than anything else. he has a crazy live arm, massive power, tons of variety...but curls too many into opponent's strike zone imo.
honestly i'd love to see goran coach shelton. he did great things for novak's serve. if he became more of a spot server...i don't think he'd need much else tbh, along w that wicked spin he'd be even more deadly and very, very hard to break.