He is not unbeatable - no one is ever unbeatable - but he's as close it comes, especially on grass. He is a genius, a magician. He is an athlete of such complete mental and physical power and calm combined that he is, I believe, unique in the history of tennis.
In winning a third consecutive Wimbledon title yesterday against Andy Roddick, he joined Bjorn Borg and Pete Sampras as the only men since the 1930s to achieve the feat. I saw both of them play, in their prime. Federer does not yet have the 14 Grand Slam titles of the record holder, Sampras, or the 11 of Borg. And he may not get them. No one knows what tomorrow will bring, when an injury or a personal crisis could change your life and end your career. But in my opinion, shot for shot, Federer is the best player who has ever played the game.
Sampras was a wonderful champion, a great, no question. But he did have weaknesses, including a less than perfect return of serve on the backhand side sometimes. And great though his mobility was, Federer's is better. He makes everything look so easy, almost effortless.
Borg was another true great, but he was a machine. He broke you down mentally. He did not overpower you in the way that Federer does. Federer's shots can be so blistering, so uncannily placed that they leave nothing to say but "How?"
We can talk about details. Federer held seven of his service games to love yesterday. He had not a single double-fault. He hit 49 winners, many of them stunning cross-court forehands from nowhere that he had any right to be, or backhands down that line that left you thinking "Holy mackerel. Awesome. How?"
If one single point exemplified what Federer did yesterday it was the first point of the seventh game in the third set, with Roddick serving. After a 16-shot rally that almost defied belief, Federer hit a running forehand rocket down the line past Roddick. Unbelievable.
But these are just details. Federer is on another level to any other player in the world right now. And when you push him, he just plays better. Not always, of course. No one can do always. But as close as it comes. He hits shots that bamboozle, confuse and defeat. He is consistently beating the very best players that the world has to offer, and beating them comfortably.
It will be no consolation to Roddick today, but it would not have mattered who Federer faced yesterday. He would have won. Roddick did not play badly. Lleyton Hewitt did not play badly in the semi-final. It's just that Federer's talent is not of this planet.
Roddick's only chance at all was to serve massively the whole time and not make a single error. He did OK, and he was coming to the net, but you cannot give Federer more than one volley because he's better than you. Simply better.
Very few people in the history of sport have such a dominance, an aura, in their prime. Muhammad Ali, Michael Jordan and Wayne Gretzky spring to mind. Federer is that good. He is so calm. His composure just does not slip. He has something within him, something so special that whatever the future brings, we should just be glad we have seen him play.