Associated Press

Tyrus Thomas. (Getty Images)

In four games this season, the fourth-year player from LSU is averaging eight points and five rebounds in 21 minutes.

Thomas, who had been battling the flu, played only 12 minutes in Chicago's victory at Cleveland on Thursday.

X-rays confirmed the a fractured radius of the left forearm Friday. Team physicians Dr. Brian Cole and Dr. John Fernandez, assisted by Dr. Mark Cohen, will perform the surgery.

With Thomas out, rookie Taj Gibson is expected to take over as a starter.

The 6-foot-10 Thomas was the fourth overall pick by Portland in the 2006 draft and then had his draft rights traded by the Trailblazers, along with Viktor Khryapa, to the Bulls for the draft rights to LaMarcus Aldridge.

Thomas started to emerge as a player last season when he averaged 10.8 points, 6.4 rebounds and nearly two blocks a game. He made 61 starts and appeared in 79 games for the Bulls.

"He tweaked his arm a little bit and he's pretty sore," Bulls coach Vinny Del Negro said before the results of the X-rays were revealed.

Chicago hosts Charlotte on Saturday.