When the ball is in the air.

It will be the sum of the outcomes of those kinds of plays spread over the course of this 16-game regular season that's going to determine the success of the 2014 Steelers.

There are other aspects to the sport – running the football, stopping the run – but even acknowledging some hiccups during this preseason, it's difficult to imagine the Steelers being difference-making awful in those, at least not to the degree necessary to sabotage an entire NFL season. Nope, the difference is going to come when the ball is in the air.

The run defense wasn't Steel Curtainesque during this preseason, with Rashad Jennings' 73-yard touchdown run in the opener and the Eagles' 182 yards and 5.2 average being especially disappointing, but the addition of Brett Keisel to the defensive line rotation and some actual game-planning of upcoming opponents will help. It's also worth noting that the history of Steelers run defense has created a skewed impression of what acceptable in this category actually is. Only 13 times in the 44 seasons since the NFL-AFL merger has Pittsburgh ranked outside the top 10 in the league in run defense, and that made 2013's No. 21 finish seem especially heinous.

But it's also worth noting that while the memory of last year's Steelers is that they were porous against the run, Pittsburgh's defense allowed 14 more rushing yards per game than Seattle's defense. Fourteen yards rushing is what separated the Steelers' defense from the Seahawks' in that category, but it's what Seattle was doing when the ball was in the air that brought a Lombardi Trophy to the Great Northwest and is the root cause of the change in the way games are to be officiated in 2014.

In today's NFL, the concept of stopping the run has given way to the reality of just being something more than paper mache against the run, because most games are won and lost when the ball is in the air.

It's usually when the ball is in the air that turnovers happen, when easy touchdowns are scored or set up by kick returns, when chunks of yards are gained or lost, when third downs either are converted or the punt team is summoned, and when touchdowns either are scored or field goals kicked. The kinds of players involved in whether those situations are successes or failures are the kind the Steelers have been adding to their defense in turning it over from the cast who won two Super Bowls in three trips over a span of six seasons, and they will need all of them to come through as this season unfolds.

The best defense also can be a good offense, and having a franchise quarterback in place is this team's primary asset. Ben Roethlisberger, probably not at the peak of his physical powers as a 32-year-old with 156 career NFL starts, still is nifty enough and strong enough to be tough to sack, and his arm remains special. And in terms of everything else that goes with the position, Roethlisberger is at the top of his game. He has a presence, a command of the offense. His leadership is respected throughout the locker room because of the way he comes through for them on the field, and these Steelers are going to need him to come through for them on the field.

Over the previous couple of seasons, the Steelers have begun with the kind of offensive unit that looked to have the potential to dominate. It didn't happen, for a variety of reasons, but this year's edition has more potential than any of those, and this is the season where it must happen. When the ball is in the air, there is Roethlisberger behind an offensive line that should be better and throwing to a primary group of five pass catchers – Antonio Brown, Markus Wheaton, Lance Moore, Heath Miller, and Le'Veon Bell – who own a sufficiently diverse set of skills to present most opponents with some matchup worries. And beyond the offensive personnel, the Steelers at last seem to have philosophical agreement on a style.

But it's the aforementioned reconstructed defense that looks to be this season's X-factor. It is younger and faster in some areas, unproven in some others. Overall, there is some personnel on hand hinting at the potential for an increased number of splash plays, but no real proven commodities besides Troy Polamalu.

Jarvis Jones has shown some aptitude for being around the ball, and Jason Worilds had seven sacks over the final eight games in 2013. Ryan Shazier and Lawrence Timmons are inside linebackers capable of being deployed as blitzers or in coverage, and if free safety Mike Mitchell duplicates the four interceptions and 3.5 sacks he posted last season in Carolina, that would represent the most production from the position in over 10 years.

But today, all of that is if, if, if. What's much more certain is the impact that splash plays – sacks and takeaways – have on a defense, and by extension on the entire team.

Back to the Seahawks for a moment. Make no mistake that Seattle is the NFL's defending champion because of its defense, a unit that finished with 28 interceptions (18 more than the 2013 Steelers), 39 takeaways (19 more than the Steelers), and 44 sacks (10 more than the Steelers). Add 19 takeaways and 10 sacks to the Steelers' 2013 defensive output, and nobody's even talking about 14 more rushing yards per game.

If they can be special when the ball is in the air, as a team, then the 2014 Steelers can become a special team. If they are not special when the ball is in the air, nothing else they do will be able to save them.