Waller extends Warsh's "play the ball, not the Fed" metaphor and repurposes it to defend his particular style of communications. He likened a central bank’s reaction function to a home plate umpire's strike zone, saying batters and pitchers don't need it to be perfect, only roughly known and stable from pitch to pitch: “Both want to play the ball, but they cannot do that until they know the umpire’s strike zone. The strike zone is the umpire’s reaction function. If the ball goes here, it’s a strike; if it goes there, it’s a ball. The players don’t expect the umpire to have a perfect strike zone—they just need a rough idea of its parameters and some guarantee that it won’t change much on every pitch. Perfection is not needed for them to play well.”(Nick Timiraos)