When game kicks off, Smith will be watching

SANTA CLARA – Alex Smith has been the undisputed 49ers’ starting quarterback since five games into 2005, his rookie season.

The only things that have kept Smith out of he 49ers’ lineup the past three seasons are injuries – until tonight.

The 49ers open the exhibition season against the Raiders at the Coliseum, and Smith will be on the sideline when the offensive starters take the field.

“It’s weird,” Smith said Thursday. “It’s definitely different.”

Smith was the 49ers’ starter when he exited the lineup last season to undergo season-ending shoulder surgery. Now, he’s fighting to retain his starting job – and trying not to consider whether a player should lose his job due to an injury.

“(I’m) just trying not to get into that, as much as possible,” Smith said. “It’s easy to get sucked in and get pissed. Obviously, they have things they’re doing upstairs, and that’s the way it’s going to be done. All I can really worry about are my reps and what I need to do.”

The biggest surprise in the 49ers’ quarterback saga is that J.T. O’Sullivan has emerged as the most serious challenger to Smith’s status as the team’s starter. The 49ers are O’Sullivan’s eighth NFL team in six seasons.

O’Sullivan has just one exhibition start to his credit. Last summer, he completed 24 of 34 passes for 232 yards with one touchdown and two interceptions in the Lions’ 37-10 loss at the Indianapolis Colts.

“It’s just great reps. You can’t diminish how important those reps are for a quarterback,” O’Sullivan said. “Whether it be in the preseason or regular-season reps with the first team against the first defense is something that you can’t duplicate on the practice field. So you have to take advantage of every situation you get an opportunity in.”

The 49ers have an open competition at quarterback, and O’Sullivan tonight gets the first opportunity to prove himself. Coach Mike Nolan said O’Sullivan will play into the second quarter.

Smith, the No. 1 overall pick of the 2005 draft, is scheduled to replace O’Sullivan and play into the third quarter. Shaun Hill might get the most action of the evening, as he is set to finish the game after entering in the third quarter.

Nolan said the reason O’Sullivan gets the opening-game starting assignment is because of a lack of familiarity with his game.

Smith has started 30 regular-season games for the 49ers, while Hill started two games late last season.

O’Sullivan is new to the 49ers. He signed a one-year, $645,000 contract with the 49ers in the offseason that included $40,000 guaranteed. He came to the 49ers based on the recommendation of offensive coordinator Mike Martz.

Martz was the Lions’ offensive coordinator last season. O’Sullivan was his backup quarterback behind Jon Kitna.

“Mike obviously said ‘I’d like to have this guy’ because we were looking for another quarterback at the time anyway and it’s always nice to find a guy that can compete with the ones that you already have,” Nolan said.

O’Sullivan has more experience in Martz’s offense than Smith and Hill. But Nolan said he sees both of those players run the offense every day. What he has not seen is O’Sullivan up close in a game environment.

“The game situation is what I’m most unfamiliar with as far as the player (O’Sullivan) goes,” Nolan said.

Nolan said he will be able to get a feel for O’Sullivan’s leadership and command of a huddle — elements that are not obvious from watching game film.

“The emotion that goes on, it’s kind of like being in the press box, as opposed to being on the field,” Nolan said of the sideline perspective. “You can feel and see the emotion that goes on in a game and you can see how guys respond to stressful situations. You can’t get that in the box and you don’t get that on TV, either.”

Receivers Bryant Johnson (hamstring) and Ashley Lelie (calf), running back Michael Robinson (knee), guard David Baas (pectoral), and safeties Mark Roman (hamstring) and Lewis Baker (thigh) will be held out of tonight’s game. Receiver Isaac Bruce will be a game-time decision, while running back Frank Gore will probably see a minimal amount of playing time, Nolan said.

You can reach Staff Writer Matt Maiocco at 521-5492 or matt.maiocco@pressdemocrat.com