Nadal completed a career Grand Slam at the US Open last month
World number one Rafael Nadal beat Canadian qualifier Milos Raonic 6-4 6-4 to reach the quarter-finals of the Japan Open in Tokyo.
Spaniard Nadal will next play Russia's Dmitry Tursunov, who beat Frenchman Richard Gasquet on Wednesday.
American second seed Andy Roddick beat Jeremy Chardy 6-4 7-6 (7-4) to set up a quarter-final clash with number five seed Gael Monfils.
Frenchman Monfils beat Italy's Andreas Seppi 6-4 6-4.
Roddick, who was knocked out in the second round of the US Open last month, said: "I'm at a point now where I'm not afraid to play long points any more.
"I haven't played much and I've struggled a little but it's nice not having to fight that mental battle. I played the big points very well. When you're playing average that's encouraging."
In other matches, Serbia's Viktor Troicki beat fourth seed Juergen Melzer 7-6 (9-7) 3-6 7-6 (7-3) to set up a quarter-final with last week's surprise Bangkok winner Guillermo Garcia-Lopez of Spain.
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