Soccer teams live and die by who controls the middle third of the pitch. Tennis has its own version of that battle, and it happens in a patch of court barely bigger than a doormat: the T. Watch any match at the US Open and you'll notice one player always seems to arrive a half-step early, while a flat, skidding ball into the corner ends points that should have gone another five shots. That's not luck. That's T-zone control — and it's trainable, whether you're a tennis player,