American Taylor Dent reached his first quarter-final in half a decade Wednesday, staging a comeback to upset fourth seed Horacio Zeballos 4-6, 6-2, 6-0 in the second round of the Atlanta Tennis Championships. Dent last got this far on the ATP in 2005 in Tokyo, when he lost to Finn Jarkko Nieminen. 'This is a big deal, I've strung two really good wins together,' said the winner. 'But I don't want to celebrate. 'My sights are set pretty high. I don't know if my goals are attainable. I'm happy with this result but I want to move forward, keep improving and advancing.' Dent, 29, who is 94th-ranked in the world, is slowly rebuilding his career after back surgery several seasons ago. His progress so far is his best since coming back to tennis in late 2008. He advanced past a second round for the first time this season. Dent, winner of four titles, survived nine double-faults in his victory lasting just over 90 minutes against Argentina's Zeballos, a semi-finalist in Houston this season. The South American had won their previous meeting at that event in April when Dent retired with hip pain. Dent called his rally 'a complete role resersal.' 'My serve picked up in the second set and things just flipped around. He rushed me in the first set and then I started making a few more balls and got him to make the mistakes. In the third set he got frustrated.' Dent claimed only his seventh match win of the season against 13 defeats and will play a fellow American Robby Ginepri or sixth seed Mardy Fish next. Michael Russell won a battle of the oldest players in the field as the 32-year- old Amkerican staged a comeback over German Rainer Schuettler, 34, to advance 1-6, 6-2, 7-5. The contest was riddled with errors and was marked by 13 breaks of serve. 