SB Nation’s Bulls blog, Blog-a-bull, keeps in brief for the immediate reaction:

Ugh, this is pretty crappy news. Tyrus was around 50% of all my Bulls enjoyment right about now (which was at about 34% overall enjoyment as it was). … no matter your feelings on Tyrus vs. Taj (either you prefer Tyrus, or are wrong), losing Thomas exposes the lack of depth on this team, and VDN gets to do all sorts of ‘coaching’ to try and compensate. This isn’t good.

Anytime Vinny Del Negro’s forced to juggle his lineup and get creative… Yes, that’s most certainly a bad situation. And while Thomas hasn’t ever been the superstar that many had pegged him as, his athleticism and boundless energy have made him fan favorite in Chicago, and huge part of what the Bulls do defensively. And since Chicago’s offense is average at best, “what the Bulls do defensively” takes on added significance. Stay tuned for more analysis and news, but yeah, pretty terrible news for the Bulls this afternoon.

(And how did it happen? “Weight training accident.” Hmm… And a “broken forearem,” you say? Could it be… Another attack of the physioball?!)

According to Inside Hoops, Bulls fourth year forward Tyrus Thomas broke his arm while weight lifting at practice this morning:

Chicago Bulls forward Tyrus Thomas suffered a fractured radius of his left forearm during a weight training session this morning at practice. X-rays confirmed the injury and he will undergo surgery tomorrow.  The surgery will be performed at Rush, by team physicians Dr. Brian Cole and Dr. John Fernandez, and assisted by Dr. Mark Cohen.

Thomas is expected to be out four to six weeks.  In four games (three starts) this season, the Louisiana State product has averaged 8.3 ppg, 5.3 rpg and 1.75 bpg in 21.0 mpg.

This news is obviously a huge disappointment for the Bulls, particularly after their upset of the Cavs last night.  Thomas is a key to the Chicago defense and someone that they'll likely have a hard time replacing. We'll have more news as it emerges from Chicago.