Federer's star has fallen a little bit, as he has now gone eight Grand Slam events without winning one. If you think we're going to see another any time soon, or even ever again, you should think twice.
This is just another loss in a series showing that Federer's days of winning Slams and dominating the tennis world are done.
If a relatively convincing loss to Nadal at the Australian Open didn't do it for you, this loss has to.
If you want to use the argument that Federer's heart may not have been completely in this match, I can grant you some validity, but not much.
For one, the Davis Cup is a big match. It is a tournament that people play in for their country. Anyone entering it is doing so with his heart completely in it. If this didn't mean anything to Federer, he wouldn't have played.
If that isn't enough, also note the opponents.
No, the Davis Cup is not the Australian Open, but John Isner is not Rafael Nadal—not even close.
Try to spin it all that you want, but Isner's win over Nadal is just another sign that Federer will never win another Grand Slam or be the world's top player.
This is an upset that can't happen to a player like Federer. When it does, it is a gigantic red flag.
The ultimate problem is that nothing can be taken for granted with Federer anymore. There was a stretch of time where he could go out and have a bad match against some of the world's best players and still win in four sets. Those days are gone and they're never coming back, and there's more to it.
This loss shows that even his early round matches are going to be a struggle. Isner may never beat him again, but there are a lot of players in the world that are just like Isner. Those guys are now all threats to Federer, and that's not even counting the likes of Nadal, Novak Djokovic and Andy Murray.
The combination of Federer's age and the rest of the world is working hard against him. He has more Grand Slams than any man in the history of the game, but that means nothing.
Jack Nicklaus isn't going to win more golf majors.
Barry Bonds isn't going to hit more home runs.
The attention will stay on Federer because of his name and past, but this loss is just another in a long two-year line of matches that show that his book has already been written.