Hitting coaches generally leave established players alone until they are asked for help. They watch them to be sure they are mechanically the same as when they are "on" and might offer suggestions if they see a flaw(meaning a change which is different depending on each players style). The manager and coach do set a tone somewhat...aggressive or patient etc that may ripple thru somewhat. New players just up and guys without solid track records get more attention but ML hitting coaches are mostly about keeping players in each individual's groove rather making wholesale changes. They are keeping the players loose watching film to nit pick inconsistencies mechanically then,alerting the player where his mechanics are off. Sometimes a guy really scuffling might ask help making a wholesale change but that is unusual. When a lineup had a lot of Ks, streaky hitters and inconsistent lines it is the players you have not who the coach is. Frazier and Votto are 2 who have praised Jacoby. It ain't Brook lunging at low off speed stuff outside when Bruce bats....nor can he change that tendency. It lies with Bruce and his ability to recognize what he is seeing. Most hitting coaches are fairly neutral when it comes to making any big improvements. They mostly strive for mechanical consistency in how each player hits. The Charley Lau or Ted K coaches who do seem to make big differences are rare. Also the idea Parker or any great hitter would make a good hitting coach is simply bogus. Ted Williams said and admitted he was a poor coach of hitting because he never understood how guys couldn't see what he did or do what he did. When you can sometimes its hard to understand why others can't. I am not defending Jacoby. I believe he is as good as most ML coaches. He ain't a hitters Brian Price, that's for sure. I think KG Sr might make a good coach but perhaps they see him as more valuable working with developing players.