Paul Sakuma, Associated Press
San Francisco 49ers quarterback J.T. O'Sullivan will open the season as the starter in front of ex-Ute and former No. 1 overall draft pick Alex Smith. O'Sullivan has been with eight teams during his career.

SAN FRANCISCO — Mike Nolan's first major move after taking over as San Francisco 49ers coach in 2005 was to select Alex Smith with the No. 1 overall pick in the draft.

Their fates have been linked ever since, from a rebuilding first year to a promising second season to last year's disappointment that led to a public spat between the two.

Now as the Niners are about to enter year four with Nolan and Smith, the coach's job is in jeopardy and the former quarterback of the future will begin the season as a backup.

Nolan officially announced last week that journeyman J.T. O'Sullivan will open the season as the starter. O'Sullivan, with his eighth NFL organization in seven seasons, got just $645,000 in a little-noticed signing early in the free agency period. But he beat out Smith, who got $24 million in guaranteed money when he signed in 2005.

"I'm very confident J.T. is at the point where he's our best man for the job right now," Nolan said.

The only thing faster than Smith's fall from No. 1 pick to probable backup has been the rise of O'Sullivan from third-string journeyman to possible starter.

He competed during offseason workouts with Smith and Shaun Hill for the starting job. But when training camp opened, Nolan essentially declared it a two-man race and O'Sullivan did not take a single snap in team drills for the first week.

O'Sullivan finally got in when Hill was sidelined by a sore shoulder and quickly became the No. 1 guy. He has worked predominantly with the first team since Aug. 6, getting his first real chance since coming into the NFL as a sixth-round pick out of UC Davis in 2002.

"Reps are cherished in this league as a quarterback, so I mean every single rep, whether it be a game or practice, I try to make the absolute most out of," he said. "So these reps have been great. Obviously everybody wants to play, so I just try to make the most of every single one."

Smith has not gotten much of a chance this summer, working mostly with the second team.

Instead of following the path of Eli Manning and Troy Aikman as No. 1 picks who became Super Bowl champs in their fourth season, Smith joins Tim Couch, Jeff George and Steve Bartkowski as the only top pick quarterbacks since the common draft in 1967 who did not start their team's opener in year four.

"I'm not thinking about that now," Smith said before the announcement was made. "When that comes, I'll deal with it. That's part of the game, too, but until then, no."

Smith hadn't had to compete for a starting job since beating out Brett Elliott as a sophomore at Utah. He began his rookie year as the backup to Tim Rattay, but moved into the starting role midway through the season.

He took every snap his second year, showing signs of why he was the No. 1 pick instead of Aaron Rodgers. But Smith injured his shoulder early last season and then had a public blowout with Nolan over the severity of the injury.

He completed only 48.7 percent of his passes with four interceptions and two touchdowns in seven starts, leading to the open competition heading into this season.

"I did have an injury and was out. Some things happened and competition is a part of this game," Smith said. "It happens everyday out here with a lot of positions. For some reason, quarterback is a position in the NFL where it doesn't happen as often especially when you are a high pick."

Nolan has said he would like to stick with his decision on a starter after being forced to use four starters last year because of injuries and ineffectiveness.

The Niners went just 5-11 with an anemic offense that was ranked last in the NFL. Nolan's decision to hire the unproven Jim Hostler as his offensive coordinator and the feud with Smith placed his job in jeopardy, but ownership decided to keep him.

Nolan is on shaky ground this year, adding even more pressure to win immediately even if he says he's not worried about his job security.

"You can be 14-2 and lose your job; you can be 2-14 and lose your job," Nolan said. "Sometimes you can be 2-14 and keep your job. I don't think about it. It's not something that you live with every day as far as coaching goes."

The quarterback debate has overshadowed every other topic in training camp, including whether defensive rookie of the year Patrick Willis will be even better at linebacker this season, how free agent acquisition Justin Smith will adjust to his new role as a hybrid pass rusher in San Francisco's 3-4 defense, and how much the Martz-designed offense will help running back Frank Gore and tight end Vernon Davis.

The play of those two will be almost as important to the offense as that of the quarterback this season. Gore's rushing total dropped by nearly 600 yards last year, but he is excited about playing in an offense that suited Marshall Faulk's skills so well in St. Louis.

"When Coach Martz came in, he told me the more I understand what he's trying to do, the more I'll like it," Gore said. "I see it. I see it. It's going to be fun this year."

Martz rarely relied on a tight end in his previous spots but also didn't have one as talented as Davis. He has 72 catches in his first two seasons, but has not been the game-changing player the Niners hoped they were getting when they selected him with the sixth overall pick in 2006.