PORTLAND, Ore. (AP) -- Dallas Mavericks center Chris Kaman did not play against the Portland Trail Blazers on Tuesday night because of a concussion.

Mavericks coach Rick Carlisle says Kaman sustained the concussion in a collision during practice on Monday. There is no timetable for his return.

Kaman is averaging 12.4 points and 6.2 rebounds this season.

The injury comes as the Mavericks have juggled their centers, starting a different one in each of their previous three games. Kaman, Elton Brand and rookie Bernard James have each taken turns. Brandan Wright also plays at center for the Mavs.

James made his second straight start on Tuesday against the Blazers.