Two of the rising stars of the men's game, Jerzy Janowicz and Grigor Dimitrov were sent crashing out in the opening round of the US Open.
Wimbledon semi-finalist Janowicz suffered a 6-4 6-4 6-2 defeat by 247th-ranked Argentinian Maximo Gonzalez, while 22-year-old Bulgarian Dimitrov went down 3-6 6-3 6-4 5-7 6-2 to Joao Sousa from Portugal.
Janowicz, the 14th seed from Poland, called the trainer onto Court 13 during the second set after having problems with his back.
He had 53 unforced errors, threw his water bottle on the court, argued with the umpire and earned the wrath of the crowd at Flushing Meadows when he resorted to serving underhand in the fifth game of the third set.
"It was like being stabbed in the back by a knife," Janowicz said of his injury. "I felt bad in my lower back. For three days I haven't been able to practice, I could barely walk.
"I was just working hard in the gymnasium when it happened. Today before the match I had injections, strong pain killers. But I couldn't serve. I just couldn't serve."
Dimitrov, who reached the third-round at the French Open this year, twice fought back from a break down in the fourth set but was outplayed in the decider by his 95th-ranked opponent.
However, Milos Raonic had no such problems against Italian qualifier Thomas Fabbiano, prevailing 6-3 7-6 (8/6) 6-3 to book a second-round date with Spain's Pablo Andujar.
The 10th seed reached the Masters series final in Montreal earlier this month and now feels he is ready to challenge at a grand slam.
"I think I can put myself in that position," said the young Canadian prospect.
"I just have to make the opportunities and convert them. I think if I play well, I can get very close if not do it. It's still a long way to go, a very long way."
In-form American John Isner raced through in straight sets against Italian Filippo Volandri, 6-0 6-2 6-3. The 13th seed blasted 16 aces on his way to victory while his compatriot Sam Querrey defeated Guido Pella from Argentina 7-6 (7/3) 4-6 6-1 6-2.
German 22nd seed Philipp Kohlschreiber came through 6-1 6-3 6-1 against young American Collin Altamirano.
There were also wins for Jarkko Nieminen, Pablo Andujar, and French trio Edouard Roger-Vasselin, Gael Monfils, and 31st seed Julien Benneteau.
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