Denis Kudla overcame third seed Jack Sock in straight sets on Thursday to reach his third ATP World Tour quarter-final at the BB&T Atlanta Open.
The Kiev-born 22-year-old qualifier converted four of five break points en route to a 7-6 (8/6) 6-3 second-round victory over his fellow American.
"I thought I served well in the big moments and played well in the key points to give myself an opportunity to be on offence," the Virginia native said on www.atpworldtour.com.
"I was really happy with my performance in the heat. It's tough to come back when it's that hot outside.
"I've been in the heat for four days now, but I'm happy to take advantage of the opportunity. It is his first match, he has no rhythm. I'm just happy for the win."
Kudla will face Dudi Sela in the last eight after the Israeli defeated eighth-seeded German Benjamin Becker 7-5 6-3.
Top seed and defending champion John Isner needed two tie-breaks to get past Czech Radek Stepanek, the American prevailing 7-6 (7/3) 7-6 (9/7) thanks in part to 33 aces.
"(The crowd support) is a huge advantage for me," said Isner, a graduate of the University of Georgia. "It doesn't guarantee anything, but the crowd and the Georgia fans really helps. It feels like I'm playing a college match. It's a comfortable match for me."
Isner will play Ricardas Berankis in the quarter-finals. The Lithuanian required just 71 minutes to topple sixth seed Steve Johnson of the United States 6-4 6-2.
Source: PA
