It's not just this season. And it's not a curse its human nature.
When a star player goes out for an extended period, other players step up and play with greater focus and the opponents may be lax and take the game for granted.
When a star player returns, the team mates can get lazy and defer to the star player and the team chemistry takes a hit for a few games... plus the opposition plays with greater focus. Not to mention, if the injured player has an injury that kept him from staying in shape, it takes time to get back in shape.
That was just one reason Phoenix was in trouble yesterday