Del Potro is better than Federer was at his age. In fact, he is at least as good as Federer is now. If DP's joints and body hold up, one cannot help but wonder if Federer's record is in jeopardy. By the way, I would say Del Potro is the better player because he won yesterday and doesn't mishit every second ball. It's absolutely crazy how often Federer misses badly these days.