There are inherent problems with having the National Football League's top defense, perhaps none more acute than trying to guard against panic when an opponent manages even a modest accomplishment. Such was the case against the Tennessee Titans, who managed to become the first team to have more than 300 yards of offense and a 100-rated passer against the Steelers this season.

"It's not the way we play defense," said outside linebacker James Harrison. "It's not the way we're used to playing defense."

The Steelers are trying to become the first team since the 1991 Philadelphia Eagles to finish the season ranked No. 1 in total defense, rush defense and pass defense. They are No. 1 in total defense and against the pass, but have slipped to No. 2 against the run behind the Minnesota Vikings.

The Vikings, however, have to play the New York Giants, who have the league's No. 1 rushing offense, so the Steelers have a good chance to reclaim that spot if they can shut down Jamal Lewis and the Cleveland Browns (4-11) Sunday at Heinz Field.

But that has been part of the problem, or, in this instance, concern.

In three of the past four games, the Steelers have allowed the opposing team to rush for more than 100 yards, something they yielded just once in the previous 11 games.

What's more, in the past three games, they allowed running backs Tashard Choice of Dallas (88 yards) and Le'Ron McClain (87) of Baltimore to post the two biggest individual efforts against them this season.

In addition, Titans rookie running back Chris Johnson had a 21-yard touchdown run against them, only the third time the Steelers have allowed a run longer than 20 yards.

While those efforts are hardly the stuff of NFL records, they represent something of an anomaly against a defense that has few seams.

"When coach [Mike] Tomlin talked to us about how we played Sunday, he said that is what a team that had a top-10 defense would do," said cornerback Deshea Townsend. "I'm sure there are a lot of teams who would love to have a top-10 defense. But, to us, it felt like our worst game ever. When that happens to us, we feel like we let everyone down."

"It's bothersome, for sure, because we pride ourselves on being tough defensively," said defensive end Brett Keisel. "We'll go back to the drawing board and we're still in position to make a run. This might have been exactly what we needed."

The Steelers want to make sure they don't have a repeat of last season, when their No. 1 defense withered down the stretch, particularly against the run.

The Steelers were ranked No. 1 across the board in defense after Week 10 last season, but finished No. 1 overall and No. 3 against the pass and run. In the final four games, they finished 1-3 and allowed an average of 373 yards offense, including 129 yards rushing.

It wasn't much better in the playoff loss to Jacksonville, either. The Jaguars had 330 yards offense, including 180 rushing.

"We're always going to find ways to get better," Townsend said. "We've been at a high level all season. To have a little hiccup, I don't sense that being a problem."

The Steelers still have an outside chance of setting the NFL record for lowest yards-per-play allowed since the 16-game season was instituted in 1978, especially against the offensively-inept Browns, who have scored just 31 points in their past five games.

After allowing the Titans a season-best 323 yards, the Steelers are allowing an average of 3.97 yards per play. The 1979 Tampa Bay Buccaneers have the record (3.89 yards).

"Lucky it happened now instead of later," Townsend said.