Hitting deep is UNDERRATED. It is, simply stated, the one thing you need to do to win. Hit consistently deep and there's essentially no way your opponent can do any damage offensively. Every tennis coach I've ever known has urged me to "miss long" rather than "miss short" in order to promote consistent depth. Watch videos of Djokovic's tremendous run last year (or Connors' entire career) and you'll see balls consistently landing just inside the baseline.