I suspect this answer will be the same for all the teams that lack the following.
Consistency at quarterback is the biggest key to the Houston Texans' success over the next three years.
Our Insiders have compiled a project in which they provide future power rankings. To accompany it, each of us is offering our thoughts on what the biggest key for future success will be to the team we cover. Houston has pieces in place to be a solid team soon. That doesn't mean things won't change a lot over the next three seasons -- in 2016 the Arian Foster and Andre Johnson eras will likely be over -- but replacing them won't be nearly as difficult as finding a consistently reliable quarterback.
You either have one, or you're looking for one. And they aren't always easy to find.
For a few years there was an overemphasis on this, given the success of men such as Peyton Manning, Tom Brady, Drew Brees and Aaron Rodgers. But all of them got beat in the playoffs this past season. The quarterback isn't the only thing that matters, but your chances for success increase significantly if you have a QB who won't cost you games.
He might be on the roster now. Perhaps Ryan Fitzpatrick will prove to be one of those late-blooming quarterbacks whose on-field decision-making improves this year. Fitzpatrick has never had a winning record, in part because of the teams around him, in part because of a preponderance of turnovers. Perhaps Tom Savage, finally staying put with one team, will develop into a long-term starter. Savage attended Rutgers, Arizona and Pittsburgh, never having a chance to get comfortable and develop. It could even be Case Keenum, who struggled mightily in his first shot at it last year, going winless in eight starts.
The point is, he hasn't been identified yet. And for the Texans to return to the top of the AFC South, he'll need to be.