SANTA CLARA – The 49ers' top offensive lineman, left tackle Joe Staley, is out for six weeks because of a sprained knee, but the only compensation the team made for the loss this week was adding another tackle to the practice squad.

Translation: In Barry Sims we trust.

Sims, the 49ers' 11th-year tackle, eased a lot of the concern over Staley's absence by filling in and playing well Sunday against Dwight Freeney and the fearsome Indianapolis pass rush. Freeney finished with a sack, but it came on a stunt, and he was not squaring off against Sims at the time.

Sims started eight games for the 49ers last season, but his hold on a roster spot seemed tenuous in the offseason. The team first added Marvel Smith with the thought that the former long-time Pittsburgh Steeler would be the starting right tackle in 2009.

When Smith retired because of a chronic back injury, the 49ers signed Tony Pashos to play right tackle. Pashos broke his shoulder against Houston and was placed on injured reserve. That made Sims the top back-up at tackle.

"There are no guarantees in this business," Sims said. "If you're not performing, you'll find yourself looking for a job. That was very clear by what coach (Mike) Singletary said, and the type of guys he was looking for. So, coming into (training) camp, I was aware that I needed to perform or I wasn't going to make this team."

If there's another injury at tackle, newcomer Chris Patrick would have to step in. Patrick on Wednesday said he played both left and right tackle in college at Nebraska and he's seen action at both positions in the exhibition season. The second-year player, however, has yet to play in a regular-season game.

The 49ers could help Sims by having tight end Vernon Davis block along the line of scrimmage, something he did heavily the past two seasons. This year, however, Davis primarily has been a receiver, and he doesn't see that changing Sunday against Tennessee.

"There's confidence to rely on Barry Sims to get it done," Davis said.

Quarterback eligible – When cornerback Tarell Brown was in school at Texas, the Longhorns had one simple rule: Don't hit quarterback Vince Young. Brown and Young will start Sunday for their respective teams, giving Brown an opportunity he's been savoring.

"I think it will be fun," Brown said. "Especially a guy I played with for three years. I have a lot of respect for him. He's been an amazing player his whole life."

Several 49ers are friends with Young, who will be making his second start of the season for the Titans. Brown considers him a good friend, while fullback Moran Norris and safety Michael Lewis are from Young's hometown of Houston.

"We're friends off the field, but once we get on the field there ain't no more friends," Brown said. "At the end of the day, I'd love to see him do a good job. I've always had the utmost respect for Vince. But once we step on the field, it's all business."

Et cetera – With defensive end Demetric Evans (shoulder) out for three weeks, rookie Ricky Jean-Francois will see his first regular-season action against the Titans. Singletary said there's also a chance that safety Reggie Smith (groin) will return to the lineup.

• Singletary said that Arnaz Battle and Brandon Jones could handle punts on Sunday.

• Singletary also said that linebacker Ahmad Brooks, who didn't see any defensive snaps in Indianapolis, would be in on more third-down situations against Tennessee.

Read Matthew Barrows' archives and blogs at www.sacbee.com/sf49ers.