Halle Westfalen - Karen Khachanov handed Japan's Kei Nishikori a second straight loss on German grass, beating the seventh seed 6-2, 6-2 on Wednesday at the ATP Halle event.

In 2017, the 36th-ranked Russian also beat Asia's top player in the second round here, when Nishikori was forced to quit with a hip injury.

Nishikori has a mixed record at the Wimbledon tune-up event, dominated over the past decade and a half by Roger Federer with nine titles.

The number 27 Japanese is coming back from wrist injury problems and working to rebuild his ranking, which once placed him firmly in the Top 10.

He began 2018 by playing a lower-level Challenger tournament before returning to the ATP in February.

The 28-year-old reached the semi-finals here in 2014 and 2015 but also exited injured in 2016 and a year ago, when he quit against Khachanov trailing 3-2 in the first set.

"I made too many unforced errors, I had a lot of mistakes," Nishikori said.

"He was playing good, but nothing special, I couldn't make a first serve and I should have stayed back more at the baseline.

"Khachanov hits a flat ball and that makes it not so easy on grass. I need to train more before Wimbledon."

Khachanov advanced to the Friday quarter-finals against Spanish fourth seed Roberto Bautista Agut, a 6-4, 7-5 winner over Dutchman Robin Haase.

Khachanov managed seven aces against his Japanese opponent, who was broken four times.

The Russian 22-year-old stands 1-1 with Bautista Agut, after splitting wins on clay and hardcourt.

Results at the ATP tournament in Halle on Wednesday (x indicates seed):

First round

Nikolaz Basilashvili (GEO) bt Rudolf Molleker (GER) 6-4, 7-6 (7/5)

Second round

Roberto Bautista Ague (ESP x4) bt Robin Haase (NED) 6-4, 7-5

Karen Khachanov (RUS) bt Kei Nishikori (JPN x7) 6-2, 6-2