Roger Federer eased into the last eight at the Cincinnati Masters after a straight sets win over Olivier Rochus.
Federer beat his former junior doubles partner 6-3 6-4 in his first event since his Wimbledon victory and will next face Argentina's Jose Acasuso.
Marat Safin showed no sign of any injury worries as he stormed into the quarter-finals.
Lleyton Hewitt and Andy Roddick also recorded straight sets wins to ease their way through.
Safin, who is making his comeback from a knee injury, defeated Slovakia's Dominik Hrbaty 6-0 6-3.
The Russian, who beat Britain's Andy Murray in the previous round, will next face Robby Ginepri, who beat Carlos Moya in straight sets.
Despite appearing to be fully fit Safin admitted his knee injury is on his mind when he is playing.
"All the time you are thinking and checking and trying not to do strange movements," he said.
"You cannot focus 100% on your game because you think of the knee.
"You cannot jump, you can jump, you can run, you cannot run. Just all the things that makes you sometimes a little bit crazy."
Hewitt, who knocked out Greg Rusedski on Wednesday, defeated Croatian Mario Ancic 6-1 6-4 in an impressive display.
A stomach bug last week forced the Australian to retire during a match for the first time in his career.
Federer v Acasuso
Safin v Ginepri
Davydenko v Hewitt
Roddick v Youzhny
He is still not fully fit but says he is getting there.
"It was a struggle early on, but it's getting better," he said. "My first couple of rounds were a bit scratchy, but this is good preparation for the US Open."
Roddick was pushed hard in the opening set but he raised his game and eased to a 7-6 (7-5) 6-2 victory over Argentina's Juan Ignacio Chela.
The American saved a break point at 4-4 before coming from a mini-break down to win the opening-set tie-break.
He broke twice in the second set to set up a meeting with Russian Mikhail Youzhny, who beat French wildcard Gael Monfils 4-6 6-1 6-1.
"I needed to get some matches in and I feel like I am competing well," Roddick said.
"I tried to be more aggressive and make him scared of my forehand. I still think there's room to improve but I am playing well."