Novak Djokovic will play in only his second semi-final of the season at the Madrid Open after Kei Nishikori withdrew due to injury ahead of their last-eight encounter.

After struggling during his opening match in the Spanish capital against Nicolas Almagro, Djokovic was back to his best in beating Feliciano Lopez in round three.

Nishikori was expected to provide a sterner test for the Serbian on Friday - despite having lost his last 10 matches with Djokovic - but a wrist problem has forced his withdrawal.

So Djokovic will get an extra day off to prepare for his last four clash with either David Goffin or Rafael Nadal - who play later on Friday.