The San Francisco 49ers will go as far as offensive coordinator Mike Martz's offense will take them this season. The club was historically bad on offense last season, and coach Mike Nolan fired coordinator Jim Hostler after one season.

Nolan surprised some when he hired Martz to take over as offensive coordinator. Martz brought in quarterback J.T. O'Sullivan, and then O'Sullivan ended up beating out Alex Smith and Shaun Hill for the starting job.

Smith was the No. 1 overall pick in the 2005 draft. The fact O'Sullivan won the job signifies a big switch in the 49ers' charted course.

When asked if the 49ers might bring back Smith next season if he weren't the starter, 49ers general manager McCloughan answered, "You can't. The amount of money we're going to invest in him, he'd have to be proven that he's the guy. When we get to the offseason, he'd have to be the guy for next year."

Smith is scheduled to make $9.625 million in base salary next season. If =

the 49ers released him, he would cost $5.3 million against the cap. Therefore, he has to at some point this season become the starter and prove that he is - without question - the team's starting quarterback in 2009.

The revamped 49ers offense opens the season Sunday against the Arizona Cardinals, and there is no telling what to expect.

"I don't have a preconceived notion of where we should be," Martz said. "I just wouldn't put a limit on it. I'm excited about this group."

The 49ers ranked last in the league last season in total offense, as well as points per game. The 49ers averaged just 13.7 points per game last season, and they're expecting to average another touchdown a game.

Martz and O'Sullivan are not the only new additions to the offense. Bryant Johnson and Isaac Bruce join the 49ers after beginning their careers with other NFC West teams. Johnson faces his former team, the Cardinals, for the first time, while Bruce played his first 14 seasons with the Rams.

"Each year we've made an effort to upgrade our wide receiver core," Nolan said. "I'm hopeful that between our top guys and the competition for the backup roles that we have a productive set of receivers."

The 49ers have one of the top running backs in the league. Frank Gore last season got off to a slow start, but he still managed to rush for 1,102 yards and added another 436 yards receiving.

"It's a talented group with great character," Martz said. "They're very unselfish and their work ethic is really good so there's really probably nothing they can't accomplish. They just don't know that yet.

It's a step-by-step process and I just wouldn't put a limit on it or a seal on it. We'll just have to see how good we can be."

Nolan is putting a lot of faith in Martz and O'Sullivan. After all, Nolan knows he has to win this season in order to return for a fifth year with the 49ers.

In selecting O'Sullivan to start, he is benching Smith, the No. 1 overall pick in the 2005 draft.

"The determining factor was, he's (O'Sullivan) probably got the better command between the three (quarterbacks) right now," Nolan said. "He played with consistency in the preseason and we moved the ball well as a unit. We scored points, we did the things that I think are really important playing that position."

SERIES HISTORY: 34th meeting. Niners lead series 19-14, including victories in both games last season. The last meeting was in Arizona, a game the 49ers won 37-31 in overtime. Defensive lineman Ronald Fields sacked quarterback Kurt Warner in the end zone forcing a fumble recovered by Tully Banta-Cain for the winning points.