American qualifier Ryan Sweeting upset US third seed Sam Querrey 7-6 (7/5), 6-4 on Thursday to reach the quarter-finals of the $442,500 ATP Delray Beach International Championships.
Sweeting won six of the last seven points, denying Querrey's fightback bid in the final game. Sweeting fell behind 0-40 but saved three break points, then rescued another with a second-serve ace before winning on his only match point.
"I feel like I'm playing good tennis," Sweeting said. "I'm one of the Americans consistently moving up, maybe not at a fast rate, but it's going in the right direction."
Sweeting, ranked 118th, advanced to a Friday date against Japan's 66th-ranked Kei Nishikori who breezed past American wild card James Blake 6-3, 6-4.
Nishikori's only ATP crown came at Delray Beach in 2008.
French eighth seed Adrian Mannarino advanced to the second round by rallying to defeat Argentina's Leonardo Mayer 1-6, 7-6 (7/3), 6-4.
Mannarino will next face Colombian qualifier Alejandro Falla and could meet US second seed Mardy Fish in the quarter-finals. Fish is the highest-ranked player in the field after US top seed Andy Roddick withdrew due to illness.
In the night match, sixth seeded Janko Tipsarevic outlasted Blaz Kavcic 6-2, 6-7 (8/10), 6-3.