Brown suffered the injury when he collided with teammate Jayson Tatum in the final minute against Portland. He was unable to put weight on his right leg while walking off the court.
The 24-year-old has followed up a breakout 2019-20 campaign with his first All-Star selection. Through 58 games this season, he is averaging 24.7 points, 6.0 rebounds and 3.4 assists while shooting 48.4 percent from the field and hitting 39.7 percent of his attempts from deep.
Jayson Tatum has been able to lead production for the team, especially in Brown's absence, but he has also missed time this year due to a COVID-19 diagnosis. When both are healthy, the Celtics attack is dominant and capable of making a run deep into the postseason.
The team is currently 34-31 and in seventh place in the Eastern Conference.
While Brown is sidelined, Marcus Smart, Grant Williams and Semi Ojeleye should see more time, though it's difficult to replace the production of the California alum.