The reigning MVP suffered the injury early in the second quarter of Game 4 on Sunday. He sprained the same ankle two days earlier in Game 3.
Bucks head coach Mike Budenholzer said Monday that Antetokounmpo was "getting treatment around the clock" to try to recover in time for Game 5. Antetokounmpo was listed as questionable on Tuesday morning's injury report.
The 25-year-old was captured on video taking jumpers during warmup a couple of hours before Tuesday's tipoff. The entirety of his pregame warmup was stationary, per Charania.
This marks Milwaukee's first playoff game without Antetokounmpo in the lineup since April 28, 2013, according to The Associated Press' Tim Reynolds.
The Bucks trail the Heat 3-1 in their best-of-seven Eastern Conference semifinals matchup.