Brad Gilbert is a former professional tennis player and Olympic gold medalist. He wrote a book about tennis strategy called Winning Ugly: Mental Warfare in Tennis, where he detailed the somewhat unorthodox strategies he used against opponents he deemed much better than himself. While I don't know much about tennis, it stressed the importance of the metagame.

The metagame isn't just about sports (or Poker, see The Raiser's Edge) – it applies to almost any pursuit. The metagame is the psychological game that exists among players, involving adjustments based on how an opponent is likely to interpret a given set of actions. It's not about playing the perfect game, it's about understanding the psychology of your opponent and using that to your advantage.