World number one and three-time defending champion Serena Williams and second-ranked Andy Murray both crashed out of the ATP and WTA Miami Open on a Monday filled with upsets. (Roger Federer Withdraws From Miami Open)
Russian 15th seed Svetlana Kuznetsova stunned 21-time Grand Slam champion Williams 6-7 (3/7), 6-1, 6-2 while British world number two Murray dropped a third-round match to Bulgarian 26th seed Grigor Dimitrov 6-7 (1/7), 6-4, 6-3. (Rafael Nadal Out in Miami Health Scare)
Williams and Murray each made 55 unforced errors, fading in the third set when it mattered most.
"A lot of unforced errors crept in and he was a lot more solid than me," said Murray, who had 22 unforced errors in the third set alone. "I made many more mistakes than usual, especially in the third set."
Williams' struggles prompted questions about her fitness and movement, irking the 21-time Grand Slam champion.
"I don't think it's appropriate to criticise my movement right now," Williams said. "I did the best I could. I can't win every match. These players come out and give their best. I have to give 300 percent every match."
The 34-year-old American was seeking her ninth Miami crown but instead matched her earliest-ever exit from 2000 with a fourth-round departure.
"It's obviously disappointing, but I have won here a lot, so it's OK," Williams said.
Also ousted were world number two Agnieszka Radwanska of Poland, upset by 20th-ranked Swiss Timea Bacsinszky 2-6, 6-4, 6-2, as well as Spanish fourth seed Garbine Muguruza, who fell 7-6 (8/6), 7-6 (7/4) to 13th seed Victoria Azarenka of Belarus.
Two-time Grand Slam champion Murray failed in his bid for a third Miami trophy and fourth final in five seasons.
The 28-year-old Scotsman dominated the tie-breaker but fell behind 4-0 in the second set and stumbled after leading in the third, swatting a forehand long on match point to fall after two hours and 24 minutes.
"It's not like I came out and played awful stuff the whole time," Murray said. "When you get your chances you have to put your foot down."
Williams, who said she was physically fine and not affected by the heat and humidity, arrived having lost back-to-back finals for the first time since 2004, falling to Germany's Angelique Kerber at the Australian Open and Belarus' Victoria Azarenka at Indian Wells.
"She struggled a little bit losing the final of the Australian Open, but she is still number one in the world," Kuznetsova said. "I don't see much to be depressed about."
But intensity only increases as Williams prepares to defend French Open and Wimbledon crowns in the next few months.
"There are expectations," she said. "There are also the expectations I put on myself. That's pretty hard to live up to, the expectations I put on myself."