Heiskanen out indefinitely with mononucleosis
Dallas placed him on injured reserve retroactive to March 2, the date of his most recent game.
Heiskanen is in the midst of an elite season with 29 points in 52 games while averaging nearly 25 minutes per night. His underlying metrics are sensational as well.
The 22-year-old is in the first season of an eight-year, $67.6-million extension he signed in July.
Dallas currently holds the second wild-card spot in the Western Conference playoff race, thanks to a 7-2-1 surge in its last 10 games.