Millsap has missed the last five games due to soreness in his right knee. Atlanta went 1-4 in his absence, including a 102-78 rout at Portland on Wednesday.
The Hawks (26-33) are three games ahead of the Detroit Pistons for the conference's final playoff spot but have lost nine of their last 10 games.
Millsap is averaging 17.6 points and 8.3 rebounds per game in his first season in Atlanta after signing a two-year, $19 million deal in the offseason. MAHONEY: LeBron vs. Durant has company: The five tightest MVP races over the last 25 years