Most offensive linemen are about as anonymous as insult-spewing blog commenters.

And 49ers backup guard Joe Looney just might be the poster boy for the faceless group.

On June 4, the day quarterback Colin Kaepernick signed his six-year contract extension, a local television station got some man-in-the-street reaction to the mega-deal. One of those men in the street? That would be the 6-foot-3, 315-pound Looney, who was identified as a “49ers fan” on the segment that appeared on KPIX-5 (click here).

Asked if the lack of recognition was a blow to the ego, Looney laughed.

“Oh, no, I don’t think much of it,” he said. “I just thought it was hilarious.”

Looney legitimately enjoyed the mix-up, but it’s conceivable his days deep in the shadows could soon end if starting right guard Alex Boone is fully committed to his contract holdout.

Boone has not participated in the 49ers’ offseason program, including the first two days of this week’s mandatory minicamp, and there are indications he won’t return until he receives an enhanced deal.

Last year, Boone hired Jonathan Feinsod and Neil Schwartz as his agents and the duo is known for their tough negotiations. In recent years, three of their clients – wide receivers Vincent Jackson and Roddy White and cornerback Darrell Revis – have held out for better contracts. In 2010, Jackson missed the first seven regular-season games.

If Boone adopts the same approach this season, Looney, 23, a 2012 fourth-round pick who has played in four career games, figures to step into his starting role. Looney has been with the first-team offensive line during offseason practices.

“Joe Looney’s done a great job,” offensive coordinator Greg Roman said. “He’s really shown himself well. I’m excited about what he’s been able to do with the opportunities. So it’s next man up. That’s just how it goes.”

That praise could be construed as a we-can-manage-without-you message to Boone. And it’s possible the 49ers could manage just fine with Looney in a starting role. Last year, he came off the bench because of an injury and played 62 snaps in a 23-13 win against the Rams, who boast one of the NFL’s best defensive lines. Looney didn’t allow a sack, a quarterback hit or a quarterback hurry, according to Pro Football Focus.

“It’s great being able to work with the No. 1 team right now, but I’ll still prepare for everything,” Looney said. “Alex is a great player. I’ve learned so many things from him. He’s a great guy. If he comes back and he’s ready to play, I’ll do everything I can just to help the football team out.”

For the moment, Looney will also continue to endure heckling from his teammates, who also found his recent television appearance amusing. Looney and Ryan Seymour, a fellow reserve offensive lineman, were both interviewed, although Seymour didn’t earn the tag “49ers fan” when he appeared on the screen.

Looney and Seymour, who were interviewed at a gas station, both initially wondered if the reporter knew they were Kaepernick’s teammates.

“Me and Seymour were kind of going back and forth with each other when we were in the car,” Looney said. “We were like ‘Do you think they knew?’ That whole situation was just hilarious.”

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Jim Harbaugh said Justin Smith hasn’t been practicing because of an undisclosed injury, but the All-Pro defensive tackle will be ready for training camp. Smith spent most of the 2013 season on the injury report with a shoulder injury. … The 49ers won’t fill their open roster spot until after minicamp ends on Thursday, Harbaugh said. The spot was created when cornerback Eric Wright retired Tuesday.