Portland Trail Blazers guard CJ McCollum did not travel with the team to San Francisco after a CT scan revealed he has a pneumothorax of his right lung, the team announced Tuesday.

A pneumothorax is a collapsed lung that occurs "when air leaks into the space between your lung and chest wall," according to the Mayo Clinic. He will undergo further evaluation.

McCollum did not play in the Trail Blazers' 102-90 loss to the Los Angeles Clippers on Monday after suffering the injury against Boston on Dec. 4. A timeline for his return has not been announced.

McCollum is averaging 20.6 points, 4.1 rebounds and 4.5 assists per game this season.

Trail Blazers backcourt injuries pile up

The Trail Blazers are already missing star Damian Lillard, who has been sidelined since Nov. 30 with abdominal tendinopathy. Lillard is scheduled to be reevaluated late this week.

Guard Anfernee Simons has missed the last two games with a sprained ankle and is considered day-to-day. Also, forward Nassir Little (ankle) has missed the last four games.

Norman Powell and Dennis Smith Jr. started Monday in place of McCollum and Lillard.

The Blazers are on a three-game skid and in 10th place in the Western Conference at 11-14.

Portland plays at first-place Golden State on Wednesday, then has three days off before a four-game homestand against the Minnesota Timberwolves, Phoenix Suns, Memphis Grizzlies and Charlotte Hornets.