MADRID, May 10 (Xinhua) -- Number one seed Novak Djokovic literally strolled into the semifinals of the Madrid Open on Friday after his rival Marin Cilic was forced to pull out ahead of their match due to a stomach virus.

Cilic's withdrawal means that Djokovic will play his sixth semi-final in Madrid against number five seed Dominic Thiem, who won a marathon match against Roger Federer 3-6, 7-6(11) 6-4.

Federer seemed to have recovered after suffering against Gail Montfils on Thursday when he won the first set 5-3, but Thiem was able to keep his nerve in the second set, which he finally won after a long tiebreak lasting 24 points.

The Austrian then took control of the third set when he broke Federer's serve in the third game but the Swiss showed his determination when he leveled the set in the eighth game.

Nevertheless Thiem then claimed his second break of the set and served out to book his place in the last four.

Number eight seed Stefanos Tsitispas defeated Alexander Zverev 7-5, 3-6, 6-2 to also book his place in the last four.

In the women's competition, two times winner Simona Halep booked her place in Saturday's final with a 6-2, 6-7(2), 6-0 victory over her unseeded Swiss opponent Belinda Bencic, who on Thursday had surprised number one seed Naomi Osaka.

Halep had looked in control in the first set, but Bencic showed good character to fight back in the second, before Halep made her stamped authority on the match in the final set.

The Romanian will attempt to clinch her third title in Madrid against Kiki Bertens after the number seven seed beat American eighth seed Sloane Stephens 6-2, 7-5.