Federer obviously has great fitness, especially for his age, but it's the relentless pressure he's putting on the opponent right now, particularly on return, which is most important. His serve for the most part has been excellent, which puts the pressure right back on the other guy. He's taking the ball early, showing great anticipation and hurrying them, making them scramble all over the place. Perhaps we should turn to Nick K's press conference for insight:
'He's just such a good -- his serve and first shot is I think by far the best on tour. I've played all the Top 4, a lot of the top guys, and his first two shots, it's so hard to do anything against. You feel like you're making a return, and then he's right on it and hits a winner. You don't get that much rhythm'