The note surfaced as a reason for Miami's upcoming decisions to make this offseason regarding three free agents and extension-eligible big man Bam Adebayo.
According to Charania, Adebayo, 23, could be costly. The Heat might pass on a new deal with cap room for Antetokounmpo in mind.
Antetokounmpo, whose 26th birthday is Dec. 6, enters the final season of a four-year deal worth $100 million in 2020-21.
What he ultimately does remains to be seen. Antetokounmpo has yet to sign an extension with the Bucks, but his most recent comments favored staying in Milwaukee.
"As long as everybody's on the same page and as long as everybody's fighting for the same thing, fighting for the same thing every single day, which is to be a champion, I don't see why not to be in Milwaukee for the next 15 years," said Antetokounmpo, whose top-seeded Bucks lost a five-game series against Miami in the Eastern Conference semifinals.
Antetokounmpo, a four-time All-Star selection, has won two consecutive NBA MVP Awards with the 2019-20 season's honor. In his seventh NBA season, he averaged a career-high 29.5 points and 13.6 rebounds, logging 30.4 minutes over 63 games as the Bucks went 56-17.