Carlos Alcaraz has been forced to pull out of Spain's team for the Davis Cup Finals with the hamstring injury he suffered on Sunday.
The world No 1 said he was heartbroken not to be able to represent his country in Bologna, dealing a major blow to Spain's title hopes.
Alcaraz suffered the problem during his final defeat by Jannik Sinner at the ATP Finals in Turin, but dismissed suggestions afterwards that he might not be able to play in the Davis Cup.
"I'm so sorry to announce that I won't be able to play for Spain in the Davis Cup in Bologna," Alcaraz wrote on social media.
"I have edema [swelling] in my right hamstring and the medical recommendation is not to compete.
"I've always said that playing for Spain is the greatest thing there is, and I was really looking forward to helping us fight for the Davis Cup. I'm going home heartbroken."
Spain begin their campaign at the Davis Cup with a quarter-final against the Czech Republic on Thursday and will now be led by 36th-ranked Jaume Munar.
"I'm not worried at all. I will have two weeks before I am playing there and I will be fully recovered on the day of the match," said Alcaraz at a press conference to promote the inaugural A Racquet at The Rock in New Jersey and
Miami Invitational events on December 7 and 8.
"This week I am going to get treatment every day. We will have specific things every day, exercises and treatment, for the next two weeks.
"I'm doing everything I can to be ready. I'm going be really serious, focused on the recovery and hopefully be as good as soon as I can."
Alcaraz's withdrawal brings to an end the most successful season of his career, with the 22-year-old winning eight titles, including the French Open and US Open, and climbing back to the top of the rankings.
"It's been really good. It's been my best tennis I have ever played. I'm really happy how I handled the pressure and grew up as a person. I learned to see the situations better on the court and mentally I am stronger," he added.
Meanwhile, Alcaraz has signed up to represent Europe at the Laver Cup in London next summer.
The Ryder Cup-style event will take place at the O2 from September 25-27, pitting Europe against the USA, whose team will include world number six Taylor Fritz.
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