Federer's loss, combined with Rafael Nadal's first-round departure and a number of other upsets, created a wide-open feel on the side opposite Djokovic's in the draw. No. 2 Andy Murray is the only player on that side left among the top 20 seeds.
But on Djokovic's side, all four players seeded to be in the quarterfinals have made it: The winner of Djokovic-Berdych will play the winner of the quarterfinal between No. 4 David Ferrer and No. 8 Juan Martin del Potro, the 2009 U.S. Open champion.
Struggling with a sore big toe, Ferrer beat Ivan Dodig, 6-7 (3), 7-6 (6), 6-1, 6-1, while del Potro overcame a painful left knee, which he hyperextended on Saturday, to top 23rd-seeded Andreas Seppi, 6-4, 7-6 (2), 6-3.
"I think in these kind of matches, in quarterfinals, all the players feel something," del Potro said.
If Djokovic is feeling anything, it isn't showing. He said his history against Haas — he was 0-2 against the German on grass — made him a little nervous coming into the match.
"I just wanted to kind of focus on my game and what I want to do," Djokovic said. "I started extremely well. That was obviously helping me to feel confident on the court."