The Bucks announced that Antetokounmpo was placed in the NBA's concussion protocol after suffering an injury in Saturday's victory over the Orlando Magic. He was initially diagnosed as having a head contusion and returned to the game.
The Bucks said Monday that "team physicians followed league protocols and consulted the league's neurologist during the evaluation periods" during Saturday's game and that Antetokounmpo "passed his neurological tests that created significant doubt that it was a concussion." On Monday, Antetokounmpo reported new symptoms and a lingering headache.
Antetokounmpo, 23, is averaging 25.0 points and 14.2 rebounds per game this season. Ersan Ilyasova will start for Antetokounmpo Monday.
"He obviously helps us a ton on both ends and does so many different things for us, so I guess it goes without saying we'll miss him a ton," Bucks coach Mike Budenholzer said. "But I think we're also excited about how we play and everybody being part of -- defensively, offensively everything we do -- and hopefully we are positioned or prepared to play with who we got."
Bucks forward John Henson is ready to step up.
"Obviously he's our best player -- one of the best players in the world -- so losing a guy like that is going to hurt us, but we're prepared for this," he said. "I worked on rebounding it and taking it coast to coast filling in for him. So it should be a good day."
The Raptors announced that they will rest Leonard on Monday.
This marks the second time in the last 10 days that Leonard will miss a game for rest. He also rested on Oct. 20 against the Wizards in the second game of a back-to-back for Toronto. Leonard played in only nine games last season for San Antonio with a thigh injury.
The Raptors, who next play Tuesday against the 76ers, also announced that forward OG Anunoby will miss Monday's contest in Milwaukee for personal reasons.
ESPN's Malika Andrews contributed to this report.