Russell suffered the injury in a loss in Utah on Saturday night and traveled back to New York with the team to undergo an MRI on Sunday. He will undergo further evaluation soon, league sources said.
Russell, 21, has been the Nets' best player this season, averaging 21 points and 5.7 assists. The Nets' backcourt has been hit hard by injuries, with Jeremy Lin out for the season with a ruptured patellar tendon and backup Spencer Dinwiddie out with a sore hamstring.
Russell was the No. 2 overall pick in the 2015 NBA draft, averaging 14.8 points and 4.1 assists in his two-plus-year NBA career.