Kei Nishikori eased into the quarter-finals of the Geneva Open thanks to a 6-4 6-3 win over Mikhail Kukushkin on Tuesday.

The world number nine has not been beyond the last-eight stage at any of his past five events and will hope to snap that run on the Swiss clay this week as he ramps up his preparations for the French Open.

Nishikori broke Kukushkin at 5-4 up to take the opening set, and raced into a 3-0 lead at the start of the second.

Four break points came and went in game six, but it mattered little as the Japanese saw out victory to set up a quarter-final meeting with Kevin Anderson, who battled past Jared Donaldson 6-3 6-7 (7-9) 6-2.

In Tuesday's first-round action, 2015 runner-up Joao Sousa saw his campaign ended at the first hurdle by Rogerio Dutra Silva, who will meet defending champion and top seed Stan Wawrinka next.

Cedrik-Marcel Stebe, Horacio Zeballos, Janko Tipsarevic and Steve Johnson were the day's other winners.