Adrian Wojnarowski of ESPN.com reported the news.
The Nets acquired Russell in the offseason in what was largely a salary dump by the Los Angeles Lakers. Los Angeles wanted to get out from under the three years remaining on Timofey Mozgov's contract, and Brooklyn smartly used the Lakers' desperation to get a player around whom it can build.
Russell is coming off an underwhelming 2016-17 season, though. His second year represented an improvement over the first but not to the extent some expected. The 2015 No. 2 overall pick averaged 15.6 points and 4.8 assists per game and shot 35.2 percent from three-point range.
He is averaging a team-high 20.9 points per game this season.
Russell's injury won't hurt the Nets too much in the short term. While the roster is stronger than it was a year ago, Brooklyn is still unlikely to contend for a playoff spot in the Eastern Conference.
Jeremy Lin's season-ending patella tendon injury already put a strain on the Nets' backcourt depth. Should Russell be out for an extended period as well, the spotlight will be on Spencer Dinwiddie.