Fifth seed Andy Murray, sixth-seeded David Ferrer and defending champion Ivan Ljubicic all fell by the wayside on a day of startling upsets at the Indian Wells ATP tournament on Saturday.
British world number five Murray was eliminated 7-6 6-3 by American qualifier Donald Young, Spaniard Ferrer crashed out 7-6 6-3 at the hands of Croat Ivo Karlovic and Ljubicic was beaten 5-7 6-4 6-2 by Argentine Juan Martin del Potro.
Spanish world number one and top seed Rafa Nadal, however, had little trouble with his opening match as he demolished South African qualifier Rik de Voest 6-0 6-2 after just an hour on the showpiece center court.
"It was a good victory for me," left-hander Nadal, champion at Indian Wells in 2007 and 2009, told reporters. "Probably my opponent played a little bit more nervous than usual.
"For that reason, it wasn't one of these matches that I had to play my best tennis. I did what I had to do to win, no?"
The early exit of Murray was the most surprising of the day's upsets, despite the fact that the 23-year-old Scot had not competed in more than a month.
Murray has always enjoyed playing at Indian Wells, where he was a runner-up in 2009, but he struggled for fluency against his 143rd-ranked opponent who won the biggest match of his career with an aggressive brand of tennis.
"Most of it was not great today," a subdued Murray said after being beaten in just over an hour-and-a-half. "I didn't serve particularly well, I didn't move very well.
"He hit a lot of winners and gained in confidence, I guess, from hitting more winners."
The 32-year-old Karlovic, whose 2010 season was cut short by six months due to Achilles surgery, powered down nine aces before sealing victory against Ferrer in 95 minutes.
The six-foot 10-inch (2.08 metre) Croat won the first set tiebreaker 7-3 and then broke his opponent in the fourth game of the second before ending the match with an ace.
"I was playing well, I was returning well and I played good on my second serve, which this year has not been the case," the 239th-ranked Karlovic told Reuters. "Today was really good."
The Croat, who broke the fastest serve world record with a 251 kph (156 mph) blast during his country's Davis Cup tie against Germany in Zagreb last week, will next meet Frenchman Gilles Simon, who beat German Rainer Schuettler 6-3 7-6.
Croat Ljubicic, who upset American Andy Roddick 7-6 7-6 in last year's final, won a tight opening set against del Potro before being broken once in the second and twice in the third.
"It was not an easy draw, of course," Ljubicic said of his opponent, a former world number four who played just three tournaments last year because of an injury to his right wrist.
"He's a great player. We had some great points and I came up short in the end. Del Potro played a solid game, as normally he does, and it was too much for me today."
Del Potro, who won his eighth ATP title at last month's Delray Beach International Championships, will next meet Ukrainian Alexandr Dolgopolov, a 6-4 6-4 winner against Romania's Victor Hanescu.
In other matches, Sweden's fourth seed Robin Soderling fended off a late fightback by Germany's Michael Berrer to win 6-3 7-6 while India's Somdev Devvarman upset 19th-seeded Cypriot Marcos Baghdatis 7-5 6-0.