Brazil coach Tite sent a message of support to Pel from the World Cup on Thursday.
Pel was hospitalised on Tuesday in Sao Paulo to regulate the medication in his fight against a colon tumor, his daughter Kely Nascimento said.
She added that there was "no emergency" concerning her 82-year-old father's health.
"We all want to wish good health to Pel," Tite said in Qatar a day before Brazil's next match against Cameroon.
Brazil, seeking its first World Cup title in two decades, reached the round of 16 after two group matches. The team needs a draw against Cameroon to finish first in Group G.
"(Pel) is our biggest extraterrestrial representative," Tite joked.
Pel was listed in stable condition after arriving at the hospital "for a reevaluation of the chemotherapeutic treatment of the tumor."
The hospital said the former great "has full control of his vital functions" and was not taken to intensive or semi-intensive care units for treatment.
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