Top seed David Ferrer survived a scare before beating local favourite Takao Suzuki 4-6, 6-3, 6-2 to reach the Japan Open quarter-finals in Tokyo on Thursday.
Second seed Andy Roddick joined him in the last eight, the big-serving American overpowering Austrian Juergen Melzer 7-6, 6-2 under floodlights.
Chasing a place at the year-ending Tennis Masters Cup in Shanghai, world number five Ferrer was given a tough workout by a player ranked 588 places below him.
"Takao surprised me," said the Spaniard, defending champion at the US $ 969,000 Tokyo tournament. "But once I broke in the second set I got more confidence and the third set was easier."
Suzuki, who came close to a shock win over Roger Federer in Tokyo two years ago, capitalised on Ferrer's early sluggishness to take first set with a fizzing serve down the middle.
Ferrer promptly stepped up a gear in the second and levelled the match with a kicking serve Suzuki could only dump into the net.
The Spaniard glided through the decider, breaking twice before wrapping up proceedings with a blistering ace after an hour and 20 minutes.
Ferrer takes on fifth seed Juan Martin Del Potro in the quarter-finals after the Argentine crushed Finnish 11th seed Jarkko Nieminen 6-1, 6-3.
Roddick, also closing in on one of the four remaining spots in next month's eight-man Shanghai shoot-out, came through safely despite a nervy first set.
"I'm glad I didn't have to spend too much time on court," said the former US Open champion, who had complained of fatigue after winning his 26th career title in Beijing at the weekend.
"I felt a bit sluggish last night but I was a lot better today."
Roddick faces Serbian Viktor Troicki in the quarter-finals after Frenchman Jo-Wilfried Tsonga retired from their match with an abdominal strain having won the first set 7-5.
Troicki was leading 2-1 in the second when Tsonga decided to stop.
Fourth seed Richard Gasquet brought Japanese teenager Kei Nishikori's run to an abrupt halt, the Frenchman racing to a 6-1, 6-2 victory in a one-sided match.
Gasquet takes on 12th-seeded Rainer Schuettler in the last eight following the German's 6-3, 6-7, 6-4 win over Russian eighth seed Mikhail Youzhny.
Chile's third seed Fernando Gonzalez overcame American Amer Delic 6-4, 7-6 to set up a meeting with ninth-seeded Czech Tomas Berdych, who upset sixth seed Tommy Robredo of Spain 7-6, 6-2.
Federer, Rafael Nadal, Novak Djokovic and Andy Murray have already qualified for the Masters Cup.