Novak Djokovic moved into the semi-finals of the Madrid Masters on Friday without hitting a ball as Kei Nishikori withdrew citing the recurrence of a wrist injury, tournament organisers said.
The Japanese world number eight missed the Barcelona Open late last month due to the injury.
Nishikori is now also a major doubt for the Rome Masters next week with 10 days to go until the start of the French Open.
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Djokovic will either renew his rivalry with Rafael Nadal or face Belgium's David Goffin in the last four on Saturday.