Pele has re-entered an intensive care unit at a hospital in Sao Paulo, with his daughter insisting he is "recovering well".
The 80-year Brazilian football legend had left the Albert Einstein hospital on Tuesday following successful surgery to remove a tumour in his colon earlier in September.
Despite concerns over his health, Pele's daughter allayed any fears over her father.
On Instagram, Kely Nascimento said: "There's already a lot of anxiety roaming the world these days and we don't want to be the reason for more.
"He is recovering well and within normal range. Promise!
"The normal recovery scenario for a man of his age, after an operation like this, is sometimes two steps forward and one step back.
"Yesterday he was tired and took a little step back. Today he took two forwards!
"I want to thank again, and always, the brilliant team here at Einstein and even more gratitude for all of the good energy that you are transmitting."
After leaving the ICU earlier this week, Pele said in a message to fans on Instagram that he was ready for "90 minutes, plus extra time."
Pele has suffered from hip problems for years and cannot walk unaided.
In recent years, he has also undergone kidney and prostate procedures.
His public appearances were already being cut before the Covid pandemic and since then he has made few unnecessary forays outside his house near Santos.
After leaving the ICU earlier this week, his daughter Kely Nascimento posted on social media to confirm the procedure had been successful and that Pele was not in any pain following the surgery.
"He is strong and stubborn and with the support and care of the brilliant team at Einstein and all of the love, energy and light that the world is sending, he will get through this," she said.
Pele won the 1958, 1962 and 1970 World Cups and remains Brazil's all-time leading scorer with 77 goals in 92 matches.