Carlos Alcaraz was troubled by injury during last week's ATP Finals in Turin. (Getty Images: Clive Brunskill)
In short:
Carlos Alcaraz withdraws from Spain's squad for the Davis Cup Finals.
Alcaraz was advised not to play after sustaining swelling in his right hamstring.
What's next?
Spain plays Czechia in the Davis Cup quarterfinals on Friday AEDT.
World number one Carlos Alcaraz says he is "heartbroken" after pulling out of Spain's squad for the Davis Cup Finals in Bologna because of a swollen hamstring.
Alcaraz aggravated the injury during the ATP Finals in Turin, where he lost to Jannik Sinner in the tournament decider on Monday AEDT.
"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 Instagram.
"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."
Alcaraz's withdrawal dealt another blow to Davis Cup organisers, the International Tennis Federation.
Sinner, ranked number two in the world, pulled out of the Davis Cup Finals last month before defending champions Italy confirmed his absence.
Italy, which has won the past two Davis Cups, will also be without world number eight Lorenzo Musetti, who withdrew citing physical and family reasons.
Musetti's place is expected to be taken by Lorenzo Sonego, who has been in Turin practising in recent days.
Italy faces Austria in the quarterfinals on Thursday morning AEDT, while Spain plays Czechia on Friday AEDT.