By Gerry Dulac

It is difficult to determine which deficiency in the offensive line is more disturbing.

Is it the run-blocking, where the Steelers have struggled to get yards for Willie Parker, despite facing many of the worst rush defenses in the National Football League?

Or is it the pass protection, which has been so bad that quarterback Ben Roethlisberger has been sacked 11 times in the past two games, despite facing teams with the lowest sack totals in the league?

"I'm not worried about the sacks," guard Kendall Simmons said. "A lot of that is trying to make plays and holding onto our blocks a little longer. The running game is what we live on, that's what we set the tone with. We just have to do a better job."

It starts in the middle.

At least, that's the prognosis of coach Mike Tomlin, who said his line has had "issues" controlling nose tackles -- a problem that was readily apparent a week ago in a 19-16 loss to the New York Jets.

It wasn't just that nose tackle Dewayne Robertson had 2.5 of the seven sacks on Roethlisberger. The Steelers also had problems running against the Jets, even though, statistically, the Jets had the worst rush defense in the league, allowing an average of 152.2 yards per game.

The Steelers rushed for only 112 yards against the Jets, 7 yards fewer than they had against the Denver Broncos, who had the league's worst rush defense when the Steelers lost to them, 31-28, Oct. 21.

Tonight, they face the Miami Dolphins, the latest team to boast the league's most porous rush defense. The Dolphins allow an average of 154.9 yards rushing per game, despite the presence of nose tackle Keith Traylor (6 feet 2, 340 pounds).

Tomlin said opposing nose tackles are creating problems for the Steelers because they are playing directly over the center, making it difficult to get double-team blocks on them.

"They usually are in a 2-gap when playing head on and they're not giving a lot of room for the guards to hit them," center Sean Mahan said. "Most of the time it's a single block and it kind of changes up some of our schemes. There is not a lot of surface for the guards to hit to start our double teams. It's not there."

Mahan said each of the teams the Steelers have played the past four weeks -- Cincinnati, Baltimore, Cleveland and the Jets -- have used a nose tackle that plays a similar style. Instead of penetrating, they engage the center and sit back, waiting to see which direction the running back will go.

"He'll just try to fall off into that area instead of us getting a normal push in one direction and have a cut-up lane for our backs," Mahan said. "It kind of takes that away a little bit."

"Just because he's running doesn't mean he's trying to penetrate," Simmons said. "He's just reading the play and looking in the backfield. Soon as the back cuts back, he's shedding the block. If he plays it right, you're not going to have any cutback lanes."

That's one of the reasons Parker has been limited the past three games, rushing for 199 yards on 69 carries (2.6 yards per carry). Without a lot of cutback lanes, he has been unable to break long runs.

And, with the exception of the Ravens, that has been against the worst rush defenses in the league. The Dolphins are another.

"I don't mind blocking big guys because you know they're not going to beat you with quickness, so you can really fire off and try to get movement," said Mahan, who is 6 feet 3, 301 pounds. "Obviously, it's harder to get movement on them because they're bigger. But we'll try to take them whatever direction they want to go. With Traylor, we'll try to keep him from falling off."