How has Nadal changed?
Finally, we need to look at the state of Federer’s one real nemesis, Nadal. As great as Rafa has been, the reality is that his physical abilities have deteriorated. He can’t play the style he used when he dominated the world of clay between 2005 and 2014. He has had too many stress-related injuries because he has to work so hard to play his absolute best. Because of that, his coach Carlos Moya has been working with Nadal to hit harder and flatter to shorten points and preserve his body. So while Nadal is regaining his old ranking after collapsing following the 2014 French Open, his new style actually hurts his results against Federer.
In AO17, when Nadal played more aggressively against Federer, his topspin forehand was only bouncing 4'1” on average, meaning that most of his ball were only going chest high. Federer has always been comfortable hitting these balls, and he dominated the first set this way. In the second, Nadal dug in and returned to his heavy topspin game. On TV, there was a graphic that showed his balls bouncing 4'11” on average - shoulder height, and it hurt “new” Federer, just like it hurt Federer in his prime. Nadal won the second set this way, then reverted to his new more aggressive style and lost the third set. Nadal dug in again, to win the fourth sets using heavy topspin, and even took a 3–1 lead in the fifth. But the physical toll was too great, and his shots either started to land to short, or he flattened out shots, and Federer stormed back, winning the last five games to win the match 6–3 in the fifth.
Most telling was the way Federer kept driving his backhand off the return of serve, as Nadal’s slice serve goes out wide, but stays low. Federer put so much more pressure on Nadal, he had break points in almost every game Nadal served in the fifth set, and broke three straight games. As I recall, he had 13 break points in the fifth set alone (remember he had only 13 break points in five sets in the 2008 Wimbledon final).
Indian Wells was even worse for Nadal. A graphic showed how he had increased the speed of his groundstrokes over the last five years in the tournament, but faster pace means a little less spin - you can’t have both. The balls were moving through the desert air very fast, and Federer consistently got to hit most of his shots chest high. In their history of matches, this was one of the worst beatings that Nadal ever suffered. He looked completely puzzled by what had happened.
https://www.quora.com/Why-was-Federer-so-dominant-before-if-his-backhand-was-weak/answer/Lon-Shapiro?srid=Xlr&share=747dcf5a
