When the San Francisco 49ers begin the 2008 preseason, the starting quarterback will be . . . J.T. O’Sullivan.

Until recently, O’Sullivan was presumed to be the third banana behind Alex Smith and Shaun Hill.  But O’Sullivan jumped back into the competition, and he’ll start the preseason opener.

According to coach Mike Nolan, however, Sullivan is getting the nod because he’s the newcomer. 

“We have experience with Shaun and Alex in game situations, and we do not have that experience with J.T. O’Sullivan,” Nolan said.

But O’Sullivan has experience with offensive coordinator Mike Martz.  And that might be giving O’Sullivan the edge, thus far.

The move doesn’t mean that O’Sullivan is at the top of the depth chart.  He’ll play the first 22 minutes of the game, and Smith will finish the first half and start the third quarter.  Hill will finish the second half.

Meanwhile, O’Sullivan took all of the first-team repetitions during Wednesday afternoon’s practice.