The short answer to the question of this thread: Injuries.
Injuries happened to Leon, which is why he's riding the pine. It also doesn't help that he's on a team that needs a scorer/star and not a scrappy hustle hard working guy.. they already have that in Varejo, who is superior.
Injuries happened to him.. it wasn't like he got exposed for being a fraud of a player or something, like some people assert here.