Defending champion Roger Federer has reached the semi-finals of the Halle grasscourt tennis championships in Germany without appearing on court, as Taiwanese quarter-final opponent Lu Yen-Huen withdrew with a recurrence of a back problem.
Federer, a six-tine winner of the tourament, now faces Japan's world number 12 Kei Nishikori, who beat American Steve Johnson 6-1 7-6, for a place in the final.
Earlier, Philipp Kohlschreiber fought his way into the semi-finals by edging past fellow-German Dustin Brown 6-4 5-7 7-6.
Kohlschreiber, the 2011 champion, now plays 69th-ranked Alejandro Falla for a place in the final after the Colombian overcame another German, Peter Gojowczyk, 7-6 7-6.
Wildcard Gojowczyk also saw his run come to an end in frustrating fashion, having claimed the scalp of third seed Milos Raonic of Canada in the previous round.
