Injuries and a thick body type are part of the inconsistency. Upton has had trouble getting through a full season without injuries, some of which have kept him off the field and some of which simply have limited him. In five full seasons he has played more than 150 games once, often hit by ailments in the second half of the season. The younger the player, the less the injury risk, so it seems odd that Upton, still without a 100-RBI season, did not start 18 percent of the games in his age 20-24 seasons.
Then there is the extreme home/road split of Upton. For a guy who early in his career was compared to Ken Griffey Jr. and Alex Rodriguez as something of a superstar prodigy, when you get him out of Chase Field he's more like Shelly Duncan.
That's just too weird. You expect some variation in home/road splits, but after more than five years in the big leagues Upton is just another guy, not a franchise player, when he's not in Arizona. Weird.