SANTA CLARA – @BigCandy83 via Twitter: thank god the season is here so I don't have to read about (Scott) Tolzien anymore. Does it really matter who the third QB is?

Answer: It's not obvious, but yes. And, brace yourself, here's one more story about Tolzien.

Alex Smith is 28. Colin Kaepernick is 24 and very much the team's quarterback of the future. The 49ers' offensive line is better than it's been in years, and it's a good bet that Tolzien, who was inactive for every game last season, will take no meaningful snaps this year, either.

A growing trend among NFL teams is to keep only two quarterbacks on the 53-man roster and stash a developmental passer on the practice squad. The third quarterback's time to shine – and to grab headlines – is the preseason. When the regular season begins, he does his work behind the scenes.

And that's likely what tipped the scales in Tolzien's favor in his competition with Josh Johnson.

Anyone who watched the 49ers' exhibition finale on Thursday probably was baffled by the team's roster decision the next day.

Johnson was excellent in showing arm strength, touch and maneuverability against the Chargers. He threw for 125 yards and two touchdowns while splitting second-half possessions with Tolzien. Johnson also ran five times for 50 yards.

It was the best preseason performance any of the 49ers' four quarterbacks had this summer. Tolzien, meanwhile, had the worst.

He underthrew a wide-open receiver, Chris Owusu, on one play and misread the coverage on another, resulting in an interception. He looked flat and ordinary. His passer rating was 15.6.

The 49ers, of course, didn't base their decision on Thursday's game. It was a culmination of all the practices, all the games and, just as important, an understanding of the third quarterback's role as a team goes through its weekly preparations during the regular season.

Tolzien leads the so-called "look" team, which runs the opposition's offense against the first-team defense in practice. This week, he'll be Aaron Rodgers. The next, he'll be Matthew Stafford, and so on.

Tolzien will scour the film of the upcoming opponent and help starting quarterback Smith find tendencies, weaknesses and strengths in the opponent's defense. During the game, he'll study the defense and offer Smith analysis when he can.

"The week's short. I mean, it goes fast," Tolzien said. "And (Smith) doesn't have time to go through every last bit of film. It's not possible. So anything I can do to complement that is for the better of the team."

On game days, Kaepernick's job as the No. 2 quarterback is to play the game mentally from the sideline. For that reason, Smith said, he tends to lean on Tolzien as a second set of eyes.

"Scott – I can definitely ask him to try to keep an eye on things and watch specifics that week," Smith said.

That's not to say that Johnson would have been bad at this. But Tolzien excels at it.

Tolzien won starting jobs in high school and college not because he dazzled coaches with his arm strength, but because he was the ultimate gym rat, the guy who knew the offense – and the opposing defense – as well as his coaches.

When the 49ers acquired him at this time last year, he lived – literally – at the team's practice facility until officials kicked him out. He slept on a leather La-Z-Boy in the players' lounge, showered in the locker room and ate at the cafeteria.

It was only logical to Tolzien: How else was he supposed to pick up the playbook in two weeks?

"I was here late nights," he said. "So I figured, why not just stay here?"

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