Delray Beach - Top-seeded Kevin Anderson quit his first-round match at the Delray Beach Open on Tuesday because of an injured right shoulder.
Anderson, who won the tournament in 2012, had just dropped the first set to 103rd-ranked American Austin Krajicek in a tiebreaker when he headed to the side-line. He packed his racket bag, shook his opponent's hand, tossed some used wristbands into the crowd and walked off.
Anderson also pulled out of the first tournament of the year in Chennai and retired from his first-round match at the Australian Open last month because of an injured left knee.
The 25-year-old Krajicek was down 3-0 in the first set but broke back on Anderson's increasingly weak serve. The 29-year-old South African was treated by the trainer after the seventh game and served for the set at 5-3 but failed to convert.
"This is just a tough start to the year," said Anderson, who served four double faults and was broken back in the fifth game of the first set. "I've been training really hard to come back (from the knee injury) and I guess I just overcompensated with my shoulder."
Krajicek was one of six Americans to advance to the second round. Rajeev Ram, the beneficiary of Anderson's withdrawal at the Australian Open, upset second-seeded Bernard Tomic 7-6 (3), 6-1, while last year's finalist, Donald Young, moved on when his opponent, Mikhail Kukushkin of Kazakhstan, retired with a leg injury while trailing 7-6 (3), 3-0.
Sixth-seeded Steve Johnson squeaked past Australian John Millman, winning 6-3, 5-7, 7-6 (8), and Sam Querrey defeated Thiemo de Bakker 4-6, 6-3, 6-4.
Former Wimbledon junior champion Noah Rubin won just the second ATP Tour-level match of his career, days before his 20th birthday, when he defeated Australian Sam Groth 6-4, 4-6, 7-6 (6).
Rubin, a wild card ranked 245th in the world, saved two match points in the 10th game of the third set - one with an ace - and a third in the 12th game before prevailing on his own third match point. At 5 feet 10 inches tall, he appeared dwarfed by his 6-foot-4 opponent but was still effective on his passing shots.
"The is definitely one of the biggest matches of my career," said Rubin, who upset world No 18 Benoit Paire en route to the second round of the Australian Open. "I was moving well and that helped. I love a target.
"I'm pretty low to the ground," Rubin adding, chuckling, "so I can be stable when I need to be."