Awful example. He was hot, he got cold....this happens to every player. He was also hot in the MLB last year. This is why you take larger samples. Things like BABIP tend to normalize, and you get a clearer picture of what that player really is in terms of expectation.
Josh Reddick is an extremely better ball player than the one month+ sample you are using to justify tossing him aside for.
Players are going to get cold, it happens, no need to run around like the sky is falling when they do. If that cold streak happens in the playoffs, so be it, you can't control that. There are several current and future HOF players who did not shine in the playoffs.