Kei Nishikori said his crushing recent defeat in the US Open final left him drained, but Japan's rising tennis star showed no hint of that Wednesday, cruising into the Malaysian Open last eight in his return to the court.

The world number eight sent Rajeev Ram of the United States packing in straight sets 6-2, 6-3.

Nishikori was dominant from the start, breaking Ram's serve and controlling the front court.

The top seed soon brought out his trademark baseline play, leaving the doubles specialist short on options.

Nishikori sealed the first set in just 22 minutes and, as his baseline work heated up, made short work of the second set as well.

"I'm feeling almost perfect. Everything worked well, my movement, my strokes. I've just got to practice tomorrow and be ready for the last eight," he said afterward.

Nishikori's stirring run in the US Open left victims including world number one Novak Djokovic in his wake as he become the first Asian man to make a Grand Slam singles final.

But he was crushed in straight sets in the final by Crotia's Marin Cilic, which Nishikori admitted took a toll, physical and mental.

"It took me a couple of days to recover from the defeat. I was disappointed to have come so far and lost, but I did great things in the tournament, beating three top 10 guys to the final.

"I certainly gained a lot of confidence from the US Open."

Nishikori will next face Marinko Matosevic of Australia, who disposed of Japan's Go Soeda 7-6 (7-5), 6-4.

Defending champion and sixth seed Joao Sousa was bundled out 7-6 (7-1), 6-2 by Germany's Benjamin Becker, while doubles top seeds Eric Butorac and Raven Klaasen fell to Andre Begemann and Julian Knowle 6-1, 3-6, 10-6.