Iker Casillas has been discharged from hospital five days after suffering a heart attack.
The Spain goalkeeper, 37, was taken ill during a training session with Porto last Wednesday and had to be rushed to hospital.
His future as a professional footballer remains unclear, but Casillas insists he feels "very lucky" and that he is "feeling much better".
"A few days ago I went through a difficult situation, something that can happen at any moment in life, but fortunately I'm fine. I am grateful and feel that I am very lucky," he said in a statement on Porto's official website.
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"Thank you to all who cared, for I felt cherished. I can only get out of this situation with a smile.
"I thank all those who helped me and who allowed the effect not to be so serious, because the FC Porto medical team responded immediately.
"I was treated very well in the hospital too.
"Thank you for the thousands of messages of support and affection I received.
"I feel much better and now it will be rest for a couple of weeks or a couple of months, I do not know, but the most important thing is to be here.
"Thank you all. I do not know what the future will be, but the most important thing is to be here, to be able to speak and tell everyone how I am and how I feel.
"Thank you very much and see you soon."
Porto signed Casillas from Real Madrid in 2015, after he had spent 25 successful years in the Spanish capital.