There was an article early in the season, maybe even spring training, that said Martinez and Coles were trying to convince Garcia to be more patient. To walk more and get his OBP up. Early in the season he had gotten his OBP up and was having better at-bats. Since then he has reverted to his old ways.
On a side note I saw comments to an article on the Phillies where a bunch of fans were calling for the dismissal of Kevin Long. Their main complaint was other than Stott, Bohm and Marsh everybody else was having a down year at the plate. I'm not sure how much a hitting coach can affect veterans like Turner, Schwarber, Harper, Realmuto and Castellanos though.