He's one of the top 5 closers in the game ...
Really? Ask the Orioles, Yankees, Angels, Astros, Dodgers, Twins and a handful of other clubs ... right now if they would trade their closer for Foulke straight up.
As a closer, you are only as good as your last 3-5 performances.
It's not a role that tolerates long "slumps."
His past track record may buy him a little more time than the average Joe, but if he continues at this rate for 1-2 weeks, I'd say his job is in jeoparady. Even if its a temporary removal from the role.