I get that but most of his problems are hitting a moving ball which more often that not, he's late on. I don't know how hitting off a tee will improve your timing. It's important to see the motion of a pitcher, his rhythm and release point consistently, over and over again. I don't know who they could use to replicate a 90+ MPH fastball during batting practice since I seriously doubt they'd use any of their own pitchers. Overall, hitting off a tee isn't going to make Davis any worse of a hitter but I doubt it will help much in his case.
Ever seen the golf drills where there is no ball being used?
Its the muscle memory that they are working on.