For most NFL teams, the loss of a franchise quarterback would be an absolutely devastating blow to their playoff hopes and dreams. It’s a quarterback driven league, and without an above-average signal caller, it’s difficult to have sustained success.

We need look no further than the Dallas Cowboys. Say what you will about Tony Romo, but since he broke his collarbone in Week 2, the Cowboys have lost three consecutive games with Brandon Weeden under center. The loss of Dez Bryant only compounded the issue, but it’s clear that without Romo, Dallas is not a playoff caliber team.

So when Ben Roethlisberger sustained a sprained MCL in Week 3, it was fair to worry about the short term future of the Steelers. Even with two of the best offensive players in the league still healthy -- Le'Veon Bell and Antonio Brown -- the unquestioned key to this offense was Roethlisberger.

And still somehow, despite very poor play from Roethlisberger’s replacement, Michael Vick, Pittsburgh is currently 4-2 and ranked 4th in terms of nERD (6.28), meaning the Steelers would be expected to beat an average opponent by 6.28 points on a neutral field.

What has been the key to their success so far, and can we expect more of the same as we move towards the heart of the regular season?

Return of the Steel Curtain?

Ok, so that I’ll admit that statement is probably a bit ambitious, but when analyzing how the Steelers have overcome a serious injury to their starting quarterback en route to a 2-1 record since then, the conversation should start with the defense.

At the start of the regular season, the Steelers’ secondary could easily have been considered the worst pass defense in the league. A lack of experience and talent appeared to be setting the stage for a weekly bludgeoning by opposing passing attacks.

Despite giving up the over 280 passing yards per game (26th most in the league), the Steelers rank 14th against the pass according to our metrics when adjusted for strength of schedule. And while the pass defense has played slightly above-average, the rush defense is near the top of the league.

Currently ranked first against the run according to our metrics, Pittsburgh has allowed just one rushing touchdown through the first six weeks of the season. The fact that teams simply cannot run the ball against the Steelers inflates the yardage allowed through the air, but both facets have combined to allow just 18 points per game, fifth best in the league.

With key pieces of the defense set to return in the near future -- Ryan Shazier, Jarvis Jones, and Stephon Tuitt -- it’s not out of the question that the defense will continue to play well and even improve over the remainder of the regular season.

A Shifting Offensive Philosophy

Prior to Roethlisberger’s injury in Week 3, the Steelers averaged nearly 350 passing yards per game compared to just 109 on the ground. Since Vick took over in Week 4, however, Pittsburgh has logically become a run-oriented offense, racking up 154 rush yards per game.

The majority of that production has come from all-world talent Bell, who has been somewhat inefficient ranking 10th in Rushing Net Expected Points (NEP) per play among 22 running backs with 70 or more carries. For a running back that finished fifth in efficiency last season among all runners with 200 or more carries, it’s possible that Bell’s production could improve, especially after Roethlisberger returns.

A causality of the switch in offensive philosophy has been the production of Brown who has not only watched his 5-catch and 50-yard streak end but who has also posted minuscule stat totals since Week 3:

This has not only frustrated fantasy owners rostering the normally ultra-consistent pass-catcher, but also Brown himself who was visibly irate at third-string quarterback Landry Jones during last week’s victory over Arizona. The chemistry between Brown and Roethlisberger is unquestioned and should lead to renewed play from Brown when Roethlisberger eventually returns.

Add in the return of the once-suspended Martavis Bryant, who went nuclear last week posting a 6-catch, 137-yard, 2-touchdown stat line, and the offense should only continue to evolve and become more balanced and dangerous as time goes on. 

Too Legit to Quit?

All things considered, the Steelers have done well to be in the position they are in. Trailing the undefeated Cincinnati Bengals by two games in the AFC North, there's still time to make up group in the standings with two head-to-head matchups against the current division leaders. Assuming Roethlisberger can return reasonably soon, and at near 100 percent health, no game on the remaining schedule is too tough to win.

The defense has been the catalyst to the 4-2 start and will be needed throughout the rest of the regular season if the Steelers intend on making a deep playoff push. The odds of a Super Bowl victory are long according to our algorithms (3.9 percent), but few teams aside from the Arizona Cardinals boast a better combination of an elite offense coupled with a young, stingy defense.

The quest for a seventh Super Bowl victory is still in its primacy entering Week 7, but considering what Pittsburgh has accomplished without the services of some cornerstone offensive and defensive pieces, it’s certainly not out of the question that this team will be playing meaningful football late into January.