Mills has been ruled out for the rest of the IPL season.
Mills featured in five games for MI this season, claiming six wickets at an economy rate of 11.17 with the best figures of 3/35 against Rajasthan Royals.
On the other hand, the 21-year-old Tristan Stubbs, who is a middle-order batter, recently made his debut for the national South African ‘A’ Squad against Zimbabwe.
“Tristan has had a very promising domestic season and played an important role for his team in the recently concluded T20 domestic league. Tristan will join the MI squad for the rest of the season,” MI said in a statement.
Mumbai Indians are enduring a dismal IPL 2022 campaign. The five-time champions have lost 8 out of their 9 matches and they are already out of the playoffs race.
The Rohit Sharma-led side will next face Gujarat Titans at Brabourne Stadium, Mumbai on May 6.