Making sure yesterday’s decision was not an indication of who’ll begin the regular season at quarterback, head coach Mike Nolan announced that UC Davis’ J.T. O’Sullivan will get the start for the 49ers in the preseason opener tomorrow evening against the Oakland Raiders. Nolan said on the team’s web-site that he expects O’Sullivan will play at least through the first quarter and possibly into the second. Alex Smith will play the remainder of the half and at the start of the third quarter with Shaun Hill finishing out the game. “I’m excited about all three of them. They’ve done a very good job,” Nolan said. “I’m not in a position to name a starter for the season. We are taking it one day at a time.” Kickoff between the 49ers and Raiders on Friday from McAfee Coliseum is set for seven p.m.