Bulls forward Tyrus Thomas had surgery on his left forearm Saturday, a day after he broke it during a weight-training session.

Coach Vinny Del Negro says the operation went well and that Thomas will be re-evaluated Tuesday. Thomas is expected to miss four to six weeks, leaving the Bulls with just 10 healthy players.

His absence could create an opportunity for rookie James Johnson, who had appeared in just one of the first five games. Del Negro says the Bulls also are discussing whether to sign another player.

Thomas is averaging 8.3 points and 5.3 rebounds.