Smith, who was shortly back after recovering from a torn ACL that he suffered while part of the Heat's G-League squad, has now endured another season-ending injury.
"You don't want to see anybody get hurt," said coach Erik Spoelstra. "But we all have such incredible deep respect for his journey, what he's had to overcome. I've been in the building all those times the last year, when nobody else was here and he was doing all the extensive treatment and rehab around the clock. He just has incredible fortitude. So you end up absolutely rooting for guys like Dru."
Smith was averaging 6.3 points, 1.6 assists, and 2.6 rebounds in 14 games this season for the Heat. He was shooting a career-high 50.8 percent from the field and 53.3 percent from beyond the arc.
In place of Smith, the Heat have given Keshad Johnson a standard two-year NBA contract.