Stopping run not a joke to 49ers’ defense

SAN FRANCISCO -- When members of San Francisco's dominant defensive line step into their meeting room, they might start off by discussing life away from football or any personal issue someone is facing. There's usually some joking around -- enough that Ricky Jean Francois has referred to this intense, close-knit group as "Looney Tunes."

The one thing that's never mentioned is an impressive streak that has gone largely unnoticed during San Francisco's remarkable turnaround season: The defense hasn't allowed a rushing touchdown this year.

If the 49ers (10-3) can keep Pittsburgh (10-3) out of the end zone on the ground tonight, they will become the first team in NFL history to go the first 14 games without giving up a rushing score.

San Francisco also hasn't allowed a 100-yard rusher in 35 straight games -- though Pittsburgh's Rashard Mendenhall, with his eight rushing touchdowns, will be determined to try to break one of those streaks.

And Pittsburgh will certainly look to run more if quarterback Ben Roethlisberger doesn't play or is limited because of an ankle injury that forced him to wear a walking boot during the week. He is listed as questionable.

"We take pride in stopping the run," 49ers defensive end Justin Smith said. "It's just one of those things, we're in the business of trying to win a football game, not necessarily streaks or stats or anything like that. The main thing is stop the run and give our team a chance to win, and that's what we're all about."

One component in the unit's success has been defensive line coach Jim Tomsula, who led the 49ers to a season-ending victory as interim coach following Mike Singletary's firing last season before being retained on Jim Harbaugh's staff.

Tomsula regularly wears a true blue-collar shirt with his name stitched into it, fitting perfectly into Harbaugh's approach of being a "blue-collar team" and not a "Hollywood team."

"If you ever see those kids in kindergarten, some of the kids take the colors and they put nice colors up and they try to draw squares," Tomsula said. "I think all the guys in my room were the ones with a big mess, a blob of stuff, you know? That's kind of the way it all is, because it's nuts in there! It's crazy!"

Maybe that's why Steelers coach Mike Tomlin called the 49ers' defense "a tough nut to crack."

San Francisco has the top-ranked run defense in the NFL, while Pittsburgh owns the No. 1 pass defense.

"They're playing good solid ball," Mendenhall said. "They're playing together and making plays."