Miami Heat star Chris Bosh has failed his physical and will not be cleared for training camp, which begins on Tuesday.
Bosh, who has a history of blood clots, took multiple medical exams this week to determine if he is healthy enough to begin practices with the team.
However, the Heat said they were unable to clear Bosh to return - putting the two-time NBA champion's career at risk.
"The Miami Heat and Chris Bosh, in consultation with team doctors and other physicians, have been working together for many months with the mutual goal of having Chris return to the court as soon as possible," a Heat statement read.
"Chris has now taken his pre-season physical. The Miami Heat regret that it remains unable to clear Chris to return to basketball activities, and there is no timetable for his return.
"We are not able to comment further in light of Article XXII, Section 3(e) of the NBA Collective Bargaining Agreement, which precludes a team from releasing certain medical information without a player's consent."
Bosh has said before that if he is not allowed to play that he will take the issue to the players' association but his former team-mate Dwyane Wade told him to focus on his health first.