Aguero faces three months on the sidelines after being treated for a heart complaint suffered during the draw against Alaves.
The Argentine posted today: "I am well and with a lot of courage to face the recovery process. I want to thank you all for so many messages of support and affection that make my heart stronger today."
Barcelona also issued a statement announcing the Argentine's long-term absence:
"The player Kun Agüero has undergone a diagnostic and therapeutic procedure by Dr. Josep Brugada. He is released and will be evaluated for the next three months for the effectiveness of the treatment in determining his recovery process."