LONDON -- Two years ago, Novak Djokovic figured out the grass at Wimbledon and found himself holding the trophy at the All England Club for the first time.
This year, by his own estimate, "I'm actually playing better tennis on grass than I played two years ago."
Top-seeded Djokovic defeated No. 13 Tommy Haas 6-1, 6-4, 7-6 (4) on Monday to advance to his 17th straight Grand Slam quarter-final. He still hasn't lost a set in the tournament.
"I feel good about myself in this moment," Djokovic said. "I'm No. 1 in the world. I have no reason to be concerned about my game."