Portland Trail Blazers guard CJ McCollum has a pneumothorax in his right lung and will be further evaluated, the team announced on Tuesday.
As a result, the eight-year pro didn't travel with the club for its matchup against the Golden State Warriors on Wednesday.
McCollum suffered the injury to his ribs on Dec. 4 against the Boston Celtics.
The team initially listed him as probable for Monday's contest against the Los Angeles Clippers before eventually ruling him out.
McCollum is averaging just 20.6 points per game this season, his lowest output since the 2014-15 campaign.