Second seed Sam Querrey came through a stern examination against South Africa's Kevin Anderson in the second round of the Farmers Classic in Los Angeles.
Querrey served for the first set at 6-5 but Anderson broke back to force a tie-breaker, which the American eventually took 10-8.
Anderson hit back in the second, breaking twice en route to taking the set 6-4, but had no answer as Querrey powered through the decider to complete a 7-6 (10-8) 4-6 6-0 win.
He will next face Rainer Schuettler, a 6-3 3-6 6-4 winner over another American, Robby Ginepri.
Third seed Marcos Baghdatis claimed his first win in five matches to advance to the quarter-finals with a 3-6 6-2 6-3 victory over Ryan Sweeting.
Baghdatis had not won a match since the French Open and looked to be slipping to yet another defeat when the American wildcard took the first set in Los Angeles.
But the popular Cypriot rallied to book a last-eight match against sixth seed Janko Tipsarevic.
"It's been a long time," Baghdatis told www.atptour.com.
"I didn't win a match on grass. It's been two months I didn't win a match. It's a long time. It feels good winning a match, even without playing good."
Tipsarevic booked his place with a straight-sets win over Indian qualifier Somdev Devvarman.
The key moment proved to be a marathon first-set tie-breaker, which Tipsarevic eventually claimed before racing through the second set for a 7-6 (11-9) 6-2 win.