It would have been the first time Murray (L) and Djokovic played against each other since Djokovic won the Doha final in 2017.
The announcement came not long before Murray was scheduled to take the court against the top-ranked Djokovic in the third round.
It would have been the first time Murray and Djokovic played against each other since Djokovic won the Doha final in 2017.
Murray had won his first two matches in Madrid, defeating Dominic Thiem and Denis Shapovalov. The former No.1 hadn't won consecutive matches since January and hadn't played in a clay-court tournament in nearly two years.
Ranked 78th in the world, the 34-year-old Murray has been making his way up the rankings since having hip surgery in both 2018 and 2019. He had arrived in Madrid with a 10-8 record in eight tournaments. He lost the Sydney final to Aslan Karatsev in January.
There were no further details on Murray’s illness. He had said after the win over Shapovalov that he was feeling fine physically.
With Murray's withdrawal, Djokovic automatically advanced to the quarterfinals - his second of the year after losing the Serbia final last month. He had lost in his first match in Monte Carlo in his first tournament on clay this season.
Djokovic is also trying to regain his best form after not being allowed to play in the Australian Open because he was not vaccinated. This is only his fourth tournament of the season. The Serb opened in Madrid with a two-set win against Gael Monfils.
Third-seeded Rafael Nadal, in his first tournament after a six-week injury layoff, takes on David Goffin, while Spanish sensation Carlos Alcaraz, celebrating his 19th birthday, faces Cameron Norrie.
Andrey Rublev, who beat Djokovic in the Serbia final, plays Daniel Evans, while defending champion Alexander Zverev meets qualifier Lorenzo Musetti. Fourth-seeded Stefanos Tsitsipas faces Gregor Dimitrov.
In the women's semifinals, eighth-seeded Ons Jabeur faces qualifier Ekaterina Alexandrova, while 12th-seeded American Jessica Pegula meets Jil Teichmann.
The 19-year-old Spaniard reached his second ATP Masters final in five weeks and claimed his first ever win over a reigning world number one, overcoming Djokovic 6-7 (5/7), 7-5, 7-6 (7/5) in front of a sell-out home crowd at the Caja Magica.
Defending champion Rafael Nadal swept past Greece’s Stefanos Tsitsipas 6-3, 6-4 to advance to his first final on clay this season at the Italian Open on Saturday. The eight-time Rome winner had been stunned by Tsitsipas, seeded eighth, in the semi-finals at the Madrid Open last weekend.
Djokovic, the world number one, had raised the alarm over an abdominal injury after his five-set battle with Taylor Fritz, but he showed few outward signs in his 7-6 (7/4), 4-6, 6-1, 6-4 win.
Nadal and Djokovic were both expected back on court to play the decisive doubles rubber that will decide which country wins the 24-nation tournament.
"Every time I get to play Rafa we get to play a lot of exciting points. There were some incredible exchanges today," said Djokovic.
Indian doubles para-shuttlers Manisha Ramadass and Mandeep Kaur grew in confidence after winning their opening match at the 4th Fazza Dubai Para Badminton International 2022 that began on Monday.
Chasing a target of 107 runs, Pakistan reached home in 18.2 overs for the loss of four wickets. Nida was the highest run-scorer for Pakistan as she remained unbeaten on 36 runs from 27 balls while captain Bismah Maroof scored 28 runs.
The stunning Al Marjan Island will again host the world’s fastest half marathon which will feature some of the best long-distance athletes, running enthusiasts.