Nishikori knocks out Monfils
Japan's Kei Nishikori ended French interest at the Gerry Weber Open in Halle on Wednesday as he overpowered Gael Monfils 6-1 3-6 6-3.
The No 4 seed, who dropped to world No 12 following his first round exit at the French Open, will now face American Steve Johnson or Russia's Teymuraz Gabashvili for a place in the quarter-finals.
While Nishikori progressed, there was a shock exit for third seed Milos Raonic as he made his earliest exit of the season, losing 6-4, 6-4 to Peter Gojowczyk.
Canadian Raonic was playing his first match of the tournament, having received a first-round bye but could not overcome the German, ranked 120th in the world.
In other second round matches, Germany's Philipp Kohlschreiber, who fell in five sets against Andy Murray in the fourth round at Roland Garros, continued his smooth start to the grasscourt season easily with a 6-2 6-4 victory over Frenchman Pierre-Hugues Herbert.
Kohlschreiber, the 2011 Halle champion, will play world No 1 and recently crowned French Open champion Rafael Nadal or Germany's Dustin Brown in the quarter-finals.
Nadal, who has a 50-13 winning record on grass and won Wimbledon in 2008 and 2010, has never been past the quarter-finals at the Gerry Weber Open as he gears up for his third attempt at a tournament dominated by Roger Federer.
The 17-time Grand Slam champion, is chasing his seventh title at Halle and reached the doubles' quarter-finals on Wednesday with compatriot Marco Chiudinelli, courtesy of a walkover over German Martin Emmrich and Italian Andreas Seppi.
Meanwhile, Colombian Alejandro Falla knocked out Dutchman Robin Hasse 7-6 (7-1) 6-4 to book his place in the last eight.