Jacobs before preseason game vs. MIN

I was standing on the field during pregame warmups as the San Francisco 49ers readied themselves to rout the Buffalo Bills. As the team trotted off the field and into the tunnel leading to the locker room before player introductions, almost everyone was smiling.

Everyone except Brandon Jacobs.

Jacobs was listed as inactive about an hour earlier, and he had a scowl going that belied a man frustrated with his role — or lack thereof — on his new team. He was not a man who was happy to be wearing standard workout clothes instead of an official uniform.

Later in the week, Jacobs turned that look into words when he spoke with USA Today’s Mike Garafolo.

Brandon Jacobs’ emotions were always in high gear during his seven seasons with the New York Giants, from the peaks of his fiery pregame speeches to the lows of his griping about his role or throwing a helmet into the stands during a game against the Indianapolis Colts two years ago.

Obviously, the idea of the San Francisco 49ers’ running back possibly facing his former team on Sunday would be enough to tap into some of that emotion. Instead, Jacobs’ response bordered on apathy.

“It would be different if things were different, put it that way,” said Jacobs, who signed with the 49ers after being released by the Giants in the spring. “I don’t have any thoughts on it.”

Jacobs has yet to dress for a game after injuring his knee in the preseason. Though he claimed he was ready to play last week, the team held him out of Sunday’s game against the Buffalo Bills. It’s clear when he talks about “certain things,” he’s referring to the fact he hasn’t been active.

“How many times have you seen me (on the field) this year?” Jacobs asked two reporters.

Zero. And after Sunday?

“Uh, I don’t know.”

Is he healthy?

“I feel great. I feel phenomenal. My leg is as fresh as yours.”

He said he was ready to go last week.

“And the week before as well.”

So it hasn’t been his call?

“No. I’m just here doing what I’ve got to do, listening to people, practicing every day. That’s all I can do,” he said.

Jacobs and Jim Harbaugh “ironed it out” soon after these comments went public, and there’s still a very good chance that Jacobs will again find himself on the inactives list tomorrow morning. But based on the opponent they’re facing there are a few good reasons to put Jacobs in uniform for the first time this season.

49ers’ offensive strengths

San Francisco’s offensive line is absolutely destroying the opposition on rushing plays. According to Pro Football Focus (who grades each player’s performance on every single play), the 49ers’ overall run blocking score of 58.6 is far and away the highest in the NFL. Chicago is in second with a total of 20.1, while the Arizona Cardinals are in last place at -39.5.

As such, it stands to reason that the 49ers should play to their strengths against the New York Giants, an average run defense that allows 4.5 yards per carry (25th in the NFL). While Frank Gore feels “like a kid” again and there is a lot to like about Kendall Hunter’s game, the 49ers are intent on not overusing Gore and Jacobs provides a different look from Hunter. Plus, there is something tempting about running the ball down the Giants’ throats and controlling the clock — Jacobs would be more helpful on that end than Anthony Dixon. That leads us to another reason…

Time of possession

The 49ers are going to have to keep Eli Manning from picking them apart, and the best way to do so — besides Justin Smith responding to offensive coordinator Kevin Gilbride’s comments from earlier in the week with his first sack(s) of the year — would be to keep the ball out of Manning’s hands. The team brought in Jacobs to help in third-and-short situations, and for all the 49ers’ strengths in 2012 they’re still No. 22 in the NFL at converting third downs at 35.4%.

An extra lift

Neither the 49ers nor Giants should have a hard time staying motivated, but with the type of fiery personality Jacobs has I can’t help but feel like seeing him run through a hole against his former team would get the crowd going, get Jacobs engaged and add a little boost to his teammates (the offensive line in particular).

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Here’s the disclaimer

Besides 5 carries for 39 yards in the first two games of the preseason, we have no idea if Jacobs has much left to offer. We have to presume he does, because otherwise the 49ers would’ve released him before the season. But if Jacobs’ knee isn’t as healthy as he says he is, or he isn’t the best back for the schemes and formations Greg Roman plans on using, there’s no reason to activate him because he isn’t the blocker Gore is and doesn’t play special teams like Dixon.