Since taking over as coordinator two seasons ago, Keith Butler has had a vision of how he wants the Steelers to play defense.

It was on display in 2016.

On Nov. 20 at Cleveland, the Steelers turned a four-man rush out of their five-defensive backs  sub-package into a sack and a forced fumble by linebacker Ryan Shazier that was recovered in the end zone by defensive tackle Javon Hargrave.

On Jan. 22 at New England, another four-man rush out of the "nickel" resulted in a Hargrave sack of quarterback Tom Brady and a subsequent punt.

There were many such examples throughout the season, particularly during the nine-game winning streak that delivered the Steelers from 4-5 to the AFC Championship Game.

But there weren't enough of them against the Patriots.

"We weren't tight enough in coverage," head coach Mike Tomlin assessed after New England's 36-17 victory denied the Steelers a berth in Super Bowl LI. "We didn't apply enough consistent pressure to the quarterback."

The Steelers had demonstrated the ability to stick with receivers and assault pockets previously.

The next step will be to do so more consistently in 2017.

But the progress made by the defense in 2016 provided a foundation upon which to continue to build.

Early in the season the Steelers struggled with basics such as tackling and being in the right gap, and with mental aspects of the game such as not trying to do too much individually and compromising the scheme.

But improvement was evident in all of those areas as the season progressed despite losing defensive end Cam Heyward for the season in a 35-30 loss to Dallas on Nov. 13.

William Gay started at right outside linebacker, Sean Davis started at strong safety and outside linebacker Bud Dupree made his 2017 debut the following week in Cleveland.

Soon thereafter, a lineup that had included Artie Burns starting at cornerback since Nov. 6 at Baltimore solidified and the defense sprouted teeth.

The Steelers amassed eight sacks on Nov. 20 in Cleveland. They picked off a pair of passes and came up with a couple of goal-line stands on Nov. 24 at Indianapolis. They held the Bills' No. 1 rushing attack to 67 yards on the ground on Dec. 11 at Buffalo.  

They were a different defense, reflected by their final regular-season rankings of No. 12 in total defense, No. 13 in rushing defense and No. 16 in passing defense.

The Steelers had been No. 21 in total defense in 2015 and No. 18 in 2014.

Projections for 2017 included Heyward's return; Burns, Davis and Hargrave coming back as second-year pros rather than rookie starters; Shazier building upon a season that saw him emerge as the only player in the NFL with at least three sacks (three-and-a-half), three interceptions (three) and three forced fumbles (three); and linebacker Ryan Shazier potentially playing next season as one of four players in Steelers' history with at least 30 career sacks and at least 10 career interceptions (Joey Porter, Greg Lloyd and Mike Merriweather are the others).

Timmons will become an unrestricted free agent on March 9, as will Harrison.

The goal of the defense, no matter the eventual configuration, will be what it's been since Butler took over in 2015.

"It's always the same formula," Butler said before the Patriots game. "We smash the run, try to put them in position to throw the ball and try to put pressure on Brady."

They'll try to do so more often next season.