Jack Sock rallies in Challenger of Dallas

American teenager Jack Sock showed some grit Tuesday to rally past 2007 tournament champion Robert Kendrick in the first round of the $100,000 yp Challenger of Dallas.

Sock played from behind for much of the first two sets but ultimately overcame an abdominal injury and his early struggles to claim a 2-6, 7-6 (7-1), 6-3 victory over Kendrick.

The 19-year-old's battling performance and the elimination of two top Americans -- No. 1 seed Ryan Sweeting and No. 3 Sam Querrey -- were the most significant Day 2 developments at the T Bar M Racquet Club.

After Carsten Ball's 6-3, 6-4 dismissal of the top-seeded Sweeting in a first-round rematch of the 2010 Dallas singles final that the Australian lefty lost to Sweeting, Querrey suffered a 7-6 (7-4), 6-3 defeat to countryman Alex Kuznetsov, who controlled the match by serving an astounding 78 percent on first serves.

Ranked No. 321 in the world and just starting his first full season on the ATP Tour, Sock left the court after the first set to receive treatment from the tournament trainer. He suffered the injury on the practice court last week and was repeatedly seen wincing on serves throughout the second set as he tried to get loose and work his way into the match.

But Kendrick's frustration -- in just his second tournament since serving an eight-month ban for testing positive for the drug methylhexanamine -- was evident after Sock won the second-set tiebreaker and turned the match.

If the wild-card entrant can get past No. 6 seed Izak Van Der Merwe in the second round, Sock will match his Challenger of Dallas quarterfinal appearance in 2011 while still a senior in high school.

The immediate exits for Sweeting (No. 76 in the world in Monday's latest ATP Tour rankings) and Querrey (85) leaves second-seeded Belgian Steve Darcis (82) as the lone Top 100 player left in the tournament. Darcis advanced to the second round with a 6-4, 6-4 victory over South Africa's Fritz Wolmarans.