Obviously, the news of Joakim Noah's surgery was a blow to the Bulls, but as we saw at the start of the season, the team survived the loss of Carlos Boozer...and similarly, the Bulls have enough to survive the 10 weeks without Noah. The loss hurts them, no doubt, but he will back for the stretch drive for the play-offs.
Coach Tom Thibodeau has indicated that Taj Gibson will get the bulk of the starts. Tom prefers to make the other teams match up to him, but there will be some opponents when Tom feels it will be better to match up to the opponent's line-up and in those cases, Omer Asik and Kurt Thomas will get some starts.
The Bulls will miss Joakim's energy. I believe that is his biggest asset that he brings to the team. When opposing centers have to chase him around and run after him from one end of the court to the other, that really wears out the other guy and that will be missed.