Novak Djokovic is starting to realize what an impact he’s making on tennis with his recent domination of Rafael Nadal — and everyone else in the game, too. Djokovic beat the top-ranked Nadal 6-4, 6-4 in the Italian Open final Sunday to stretch his unbeaten start this year to 37 matches. Djokovic trails only John McEnroe’s 42-0 start in 1984.