Since he became Steelers head coach in 2007, Mike Tomlin has never seen his defense look as it did in 2013.
It wasn't just the horrid statistical appearance of leading the league in most 50-yard plays allowed and ranking 21st against the run.
It was the actual look of the defense, too.
The Steelers used their sub-packages in which they employ five or more defensive backs nearly 65 percent of the time -- an increase of 10 percent from the previous season, Tomlin said.
They used the packages so frequently to combat what has become a growing trend in the league: Multiple-receiver formations in which opposing offenses try to spread the field.
Problem is, that takes the Steelers out of their base 3-4 formation way too often and creates opportunities for teams to run the ball more efficiently. That's one of the reasons why the Steelers allowed an average of 4.3 yards per rush attempt, their highest in 14 years, and gave up 18 rushing touchdowns -- nearly four times as many as they allowed in their most recent Super Bowl year in 2010 (5).
"It has changed over the years," general manager Kevin Colbert said. "It has become more passing, more sub-package defenses. It has increased because of the change offensively. It doesn't change the way we evaluate. In a 3-4 defense, you are still going to start with a nose tackle."
Nose tackle is arguably the second-most important position in the Steelers defense, right behind outside linebacker. It was especially true in Bill Cowher's defense, where the Steelers invested a No. 1 draft choice in Casey Hampton in 2001 to be their immovable object in the middle for 12 seasons.
Hampton was the prototypical "zero technique," the player who would eat up blocks and create room for the linebackers to make plays. He was the anchor of their 3-4 defense.
But, according to Colbert and defensive end Cam Heyward, the value of the nose tackle in the Steelers defense remains the same today, even though a player such as Hampton would be spending even more time watching from the sideline in the modern NFL.
The 2013 season was the first without Hampton, who was not re-signed. They turned the job over to Steve McLendon, who played a different style than their former five-time Pro Bowl nose tackle, and the results were not surprising. Teams ran easily through the interior of the Steelers defense, something they haven't been able to do in a long time.
It's one of the reasons the Steelers brought in big-bodied Cam Thomas (6 feet 4½, 330 pounds) from the San Diego Chargers in free agency (Colbert said Thomas will be used at end but also could play in the middle). And why they likely will look to the early rounds of the draft to reinforce the interior.
"I think it's the most critical position on our defense in the run," said Heyward, a former No. 1 choice who enters his fourth season as a star on the rise. "I think our nose tackles have to be ready to play in sub-package this year. Steve can rush, Cam can rush, and we're looking for them to add more to this defense."
The Steelers have the 15th overall pick in the draft and are looking to strengthen one of two positions in the first round -- wide receiver or cornerback. Early mock drafts had the Steelers taking Notre Dame nose tackle Louis Nix III with the first pick, but taking a player who would be used only 35 percent of the time in the first round does not make a lot of sense on many fronts.
For example, McLendon played only 355 snaps in 14 games in 2013 (he missed two games because of ankle injury), an average of 25.4 snaps per game. The most snaps he took in any one game was in Oakland, when he appeared for 40 plays after the Raiders took a 14-0 lead in the first quarter.
But the Steelers defense averaged 68.3 snaps per game in 2013, meaning McLendon played 37.1 percent of the time. As the season wore on, that number dwindled. McLendon averaged just 15.3 snaps in the final six games he played, though that number could have been affected by the injury that caused him to miss the Nov. 28 game in Baltimore and the Dec. 15 game against Cincinnati.
That points up the conundrum confronting the Steelers: How to stop the run while mostly playing a defense with at least five defensive backs? It has been their No. 1 priority in the offseason.
"I think it's just got to be everybody on the same page," Heyward said. "I think we had a lot of technical issues, a lot of execution issues. It's a new defense and we expect that we don't make the same mistakes anymore and we have to limit those big plays. [We gave up] too many this past year and that's our main goal."
But, in sub-package football, the Steelers typically take their nose tackle off the field. That, though, could force them to seek a lineman who is something of a hybrid -- someone with the size to play inside but the ability to play defensive end. That's what they got with Thomas.
Candidates outside the first round who fit that profile are LSU's Ego Ferguson (6-3, 315) and South Carolina's Kelcy Quarles (6-4, 297). They each have the strength to play inside and could be available in the third round, though the Steelers only have a compensatory pick in the third round.
"The nose tackle position is vital," Heyward said. "Not having a guy like Steve on the field, they're going to want to run the ball. But when we have Steve on the field, or Cam or whoever is in there, it makes a big difference. I think it's the most critical position on our defense in the run."
Added Colbert: "You have to get to third down and second-and-long. If you don't have that player help you get to those extended downs then you are going to have problems. Nose tackle will always be important to our defense."
Gerry Dulac: email@example.com and Twitter @gerrydulac.