PITTSBURGH — Mike Tomlin offers two words of advice for those who would rush to judgment on the Pittsburgh Steelers’ running game: Be patient.

The Steelers ran for a paltry 36 yards on 23 carries while beating Tennessee 13-10 on Thursday, their lowest output in a season opener in nine years. Willie Parker appeared a bit slow and tentative in getting to the line of scrimmage, and Rashard Mendenhall looked confused at times.

So did an offensive line that, according to left tackle Max Starks, had trouble adjusting to some fronts offered by Tennessee’s 4-3 defense. Most of the Steelers’ AFC opponents use a 3-4 system.

Despite the Steelers’ uncharacteristic ineffectiveness in running the ball, Tomlin said looking for ways to explain away the problems or pointing fingers won’t lead to improvement.

“You know, it’s a factor,” the Steelers coach said Tuesday of the 4-3, which is also played by Chicago, this week’s opponent. “I’m not going to allow it to be an excuse. We have to execute and play winning football, and we’re capable of that. We understand what we face schematically this week and how they play, but at the same time understanding and being able to function against it are two different things.”

It’s probably not helping that Parker was limited by injuries to four carries in the preseason, or that Mendenhall had precious little time in the offense last year until going down with a season-ending shoulder injury after four games.

To Tomlin, developing a run game — even one as consistently good as Pittsburgh’s — is an evolving process that sometimes takes more than one week.

“I believe, particularly in September football, people make a commitment to stopping the run and it’s easier to make the commitment when everybody feels good and you’ve got all the horses in the stable,” said Tomlin, a former Vikings defensive coordinator. “I think over the course of a long haul, you see who’s good at it week in and week out. It’s usually tough sledding early in the football season. That’s been my experience.”

Someone who knows Pittsburgh’s running game as well as anyone, although he did not play under Tomlin, believes the Steelers (1-0) will have ongoing problems running the ball.

Jerome Bettis, the No. 5 runner in NFL history, called the Steelers “a mediocre running team on their best day” in a weekly column he is writing for Web site SI.com. Bettis played for the Steelers from 1996-2005 and is the second-leading rusher in franchise history.

“I don’t think they’ve reached a panic situation yet because the Titans don’t allow anyone to run the football on them,” Bettis wrote. “But there are serious problems. Willie Parker: I haven’t seen much from him. Rashard Mendenhall: I haven’t really seen him, period. ... The running back I like least on the team is Frank Summers, the rookie fullback. He doesn’t seem to understand what’s going on. He’s missing plenty of blocks and that’s affecting everything. This definitely has to be addressed off the field this week.”

Summers is a fifth-round draft pick from UNLV who was outplayed during training camp and in the exhibition games by non-drafted rookie Isaac Redman, who is currently on the practice squad. Summers did not have any carries against Tennessee.

Bettis also wrote that the offensive line lacks continuity and “on top of not being able to protect Ben Roethlisberger, they’re letting running backs get hit before they reach the line of scrimmage. There’s not a lot any back can do in that situation.”

Despite winning the Super Bowl last season, the Steelers ranked only 23rd in rushing and did not have a 1,000-yard runner as Parker was bothered by knee and shoulder injuries.

Parker, who has rushed for 1,000 yards in three seasons and is unsigned past this year, expects the practices before Sunday’s game against the Bears (0-1) to be unusually demanding.

“We just got to clean up the technique and clean up the little things,” he said. “We’ve got to practice hard and practice full speed. We’ve all got to account for one another. We’ve got to clean up what we did the last game.”