(CNN) -- Veteran Tommy Haas described his fourth round victory over world No. 1 Novak Djokovic at the Miami Masters as "one of the best wins of my career".
The German, who reached No. 2 in the world rankings in 2002, kept his cool to become only the second player this year to beat double defending champion Djokovic in an ATP Tour event.
The 6-2 6-4 triumph was Haas' third win over six-time grand slam winner Djokovic in seven career meetings and his first win against a top-ranked player since he beat Andre Agassi in 1999.
"I'm just really happy and proud of that tonight, against such a great player who has been dominating the sport the past couple of years, I really took advantage of the opportunities I've gotten," the 34-year-old German told the tournament's official website.
"I think I played extremely well. He gave me a lot of looks, and I took advantage of it."
"These are the moments I appreciate the most, going on those big stadiums, big stages, playing against the best people in the world. Playing against someone like Novak and coming out on top at this time of my career, it's unbelievable."
Djokovic was magnanimous in defeat, praising his opponent while also admitting he was well below his own exceptionally high standards.
"All the credit to him," said the Serb, who also lost to Juan Martin del Potro at the recent Indian Wells Masters event. "He played a great match and he was the better player, no question about it.
"The results show everything. As far as I'm concerned, it's definitely the worst match I have played in a long time."
Haas advanced to play French 11th seed Gilles Simon, in what is the first all-European quarterfinal line-up in the event's history.
Djokovic's defeat means second seed Andy Murray is the highest-ranked player left in the draw.
The 2012 U.S. Open champion breezed beyond Italy's Andreas Seppi to set up a last-eight meeting with Croatia's Marin Cilic, who upset fifth seed Jo-Wilfried Tsonga.
No. 3 David Ferrer won in straight-sets against Japan's Kei Nishikori, cruising to a 6-4 6-2 success. Spain's Ferrer will play Austria's Juergen Melzer for a place in the semifinals.
The quarterfinal line-up is completed by fourth seed Tomas Berdych and Frenchman Richard Gasquet, who defeated Sam Querrey and Nicolas Almagro respectively.