Sergio Aguero has been ruled out for at least three months with a heart problem.
The Argentine forward had to come off after appearing to suffer from breathing difficulties in Barcelona's 1-1 draw against Alaves on Saturday.
He was subsequently diagnosed with a heart arrhythmia.
Barca released a statement on Monday evening revealing he will be out of action for a few months.
"Barcelona player Kun Aguero has been subjected to a diagnostic and therapeutic process by Dr. Josep Brugada," Barcelona said in a statement.
"He is unavailable for selection and, during the next three months, the effectiveness of treatment will be evaluated in order to determine his recovery process."
The 33-year-old has taken to social media following the news.
"I am well and in good spirits to face the recovery process. I want to thank you all for so many messages of support and love that make my heart stronger today," he wrote on Twitter.
Aguero's time at Barcelona has not gone to plan.
The Argentine was expected to be Barca's first-choice striker after joining on a free transfer from Manchester City in the summer.
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But he picked up a calf injury before he even played a game for the club, ruling him out for the first few months of the campaign.
Aguero made his return at the start of October. He made five appearances, scoring once, before having to come off after 40 minutes played against Alaves.
We wish him all the best and a speedy recovery.