he has a chronic back issue among other things. "not supposed to" happens quite a bit, it's baseball. He's a bust, but let's not pretend like he was some big malcontent. When he played, for the most part, he was a solid starter and sometimes more.
I think the biggest bust is Eloy personally. A golden bat that was pretty much penciled in as at worst a 280/340/500 type that would put up 35 HR a year in the Cell with a 2-3 WAR floor.
Dude isn't even replacement level and can't hit 25 HR a year.