Ben Simmons tried to round himself into playing shape but hit a speedbump.
Simmons is dealing with back pain that came up during the reconditioning process.
The issue will require further strengthening of the area over a period of time before he can return to action.
Nets head coach Steve Nash told reporters that Simmons had not yet taken part in a high-intensity workout.
Simmons hasn't appeared in a game this season after a drama-filled start to the year.
The 25-year-old was traded to Brooklyn in a deadline deal that sent James Harden to the Philadelphia 76ers. He told the team he wanted to be traded after being the subject of trade speculation.
Simmons said in October that he wasn't mentally ready to compete with the team. The team finally agreed on a trade after the first four months of the year.
Brooklyn has been patient with the talented player, keeping him out due to return to competition conditioning.
The Nets need Simmons production as they try to climb their way out of the Eastern Conference cellar. They have lost eight of their last 10 games and are currently the No. 8 seed with a 31-29 overall record.
In a down year, the three-time All-Star has averaged 14.3 points, 7.2 rebound and 6.9 assists per game, even in a down year. He was named first-team All-Defense for the second year in a row.
Until Simmons is at full strength, the backcourt will continue to be handled by Seth Curry and Patty Mills.