Madrid - 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 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.
"I will plan to play Rome, but we'll see." said the Japanese.
"I cannot promise to play or pull out right now.
"(The) French is more important."
Djokovic will either renew his rivalry with Rafael Nadal or face Belgium's David Goffin in the last four on Saturday.
In the Women's Madrid Open defending champion Simona Halep cruised back into the final for the third time in four years with a 6-2, 6-3 over Latvia's Anastasija Sevastova.
Halep also thrashed the world number 22 two weeks ago in Stuttgart and there was never any danger of an upset as the Romanian reeled off five straight games to close out the opening set.
Sevastova hinted at a fightback early in the second as she got out to a 3-0 lead.
But Halep, who is also into the semi-finals of the women's doubles with compatriot Irina-Camelia Begu, showed no signs of lacking in energy as she bounced back in emphatic fashion to win the last six games for the loss of just 14 points.
Halep with face on form Frenchwoman Kristina Mladenovic or Svetlana Kuznetsova in Saturday's final.
Novak Djokovic (SRB x2) bt Kei Nishikori (JPN x6) - retired
Simona Halep (ROM x3) bt Anastasija Sevastova (LAT) 6-2, 6-3