Two-time defending champion Novak Djokovic crashed out in the fourth round of the Miami Masters on Tuesday while last year's runner-up Andy Murray eased through to the quarter-finals in straight sets.
World number one Djokovic was stunned 6-2, 6-4 by German 15th seed Tommy Haas but US Open winner Murray had no such difficulties, breezing past Italy's Andreas Seppi by the same score in the $8.5 million ATP and WTA hardcourt event.
"There are days when you don't feel good on the court and this is one of those days," Australian Open champion Djokovic said.
The Serb lost for just the second time this season, never getting to grips with Haas, who kept Djokovic off his game with a number of skillful shots.
"All the credit to him. He was the better player. As far I am concerned it is the worst match I have played in a long time," Djokovic said.
"I just didn't feel good on the court. The conditions were different. The balls didn't bounce at all and he used a variety of shots very well."
"I just didn't find a solution to come back into the match."
Haas, who turns 35 next week, advances to the last eight where he will face Frenchman Gilles Simon who outlasted Djokovic's countryman Janko Tipsarevic 5-7, 6-2, 6-2.
"I had the mentality tonight going out there believing in it," Haas said. "You've got to. I had a good game plan."
Haas hit seven forehand winners and won 76% of his first-serve points, snapping Djokovic's 14 match-winning streak in Miami.
Haas easily won the first set then clinched victory on his second match point with a forehand winner to the open court, ending the 80 minute match.
Djokovic, who had won this event three times (2007, 2011, 2012), had one double fault and won just 54 percent of his second serves.
This is the first time since 1999 Haas has beaten a world number one. He defeated Andre Agassi in three sets at the Grand Slam Cup for his only other win over a world No. 1 in 15 contests.
Scotsman Murray, the 2009 Miami winner who lost to Djokovic in last year's final, needed only 86 minutes to book a date in the last eight with ninth seed Croatian Marin Cilic.
World number three Murray only lost three points (28/31) on his first serve all match. He also fired three aces and had two double faults.
"Today I served well," Murray said. "When I was down in games I served pretty good, too.
"I just keep working on it each day. Focusing hard on each serve specifically."
Cilic advanced with a 7-5, 7-6 (7/4) win over French sixth seed Jo-Wilfried Tsonga.
Spanish third seed David Ferrer advanced to the quarter-finals with a 6-4, 6-2 victory over Japan's 13th-seeded Kei Nishikori.
He will play Austria's Jurgen Melzer, who defeated Spain's Albert Ramos 2-6, 6-3, 6-3.
French eighth seed Richard Gasquet outlasted Spanish 10th seed Nicolas Almagro 6-7 (3/7), 7-5, 7-6 (7/3) and will next face Czech fourth seed Tomas Berdych, who dispatched US 17th seed Sam Querrey 6-1, 6-1.
In the women's draw, world No. 1 Serena Williams beat China's fifth seed Li Na 6-3, 7-6 (7/5) to book a semi-final tie against Polish fourth seed Agnieszka Radwanska who rallied to beat Kirsten Flipkens, of Belgium, 4-6, 6-4, 6-2
Breaking Li three times in each set, Williams fell behind in the second set before roaring back to hold off Li, taking the last point off the Chinese's star's serve to end matters after one hour and 50 minutes.
"It's good to be able to at least come back," Williams said. "I like to believe that I try to be a solver. I just try to do things different if something is not working."
Williams had three aces and six double faults to one ace and seven double faults for Li.
"I just can't hit any more double faults," Williams said. "It's embarrassing and unprofessional. I hit about 50 in one game and it was just outrageous. It was like at this point I shouldn't be a professional tennis player."
Williams won Miami titles in 2002, 2003, 2004, 2007 and 2008 and is trying to become the first six time winner.