I've heard mustard applied to sports for a long time but maybe not for a long time.
The Fastball: It is called such because it comes at the hitter with some mustard on it. Don’t worry this is not in the literal sense. That would be illegal, especially these days. Remember you aren’t allowed to apply a foreign substance to the baseball. What we are discussing in the case of a baseball with mustard on it is the fastball. Mustard applied to a baseball means, figuratively, that it is coming at the hitter at an increased rate. The idea is to throw the ball fast enough to prevent it from being hit.
