The 2018 season is important for the team, for Dave Martinez (left) and for Mike Rizzo. (Jonathan Newton/The Washington Post)

Idealistic baseball people associated with reliable winning baseball do not like to discuss the notion of a window. Windows can be flung wide open with good player development. Even as they slide close, they can be propped open with a big trade or acquisition. Sometimes, they can even be kept ajar with a little luck here and there. In other words, don’t put a time limit on an annual contender’s ability to contend annually. The smartest ones won’t let their window close.

Perhaps the Washington Nationals can maintain a healthy aperture, even if a few keystone stars head elsewhere. But they cannot avoid the threat of a recession entirely, and the choices they make in 2018 will likely decide the fate of their next half-decade, if not more.

If that sounds overly dramatic, or like a hunt for New Year’s Day intrigue in the barren winter wasteland of baseball … well, to some extent you heard correctly. The Nationals have control of several budding or established stars for at least two seasons and beyond. Anthony Rendon, Trea Turner, Ryan Zimmerman, Max Scherzer, Sean Doolittle, Michael A. Taylor, Adam Eaton, Victor Robles, Tanner Roark and others are all under control for long past 2018.

But after the 2018 season, the Nationals will have to face life without their two biggest middle-of-the-order bats — Bryce Harper and Daniel Murphy. They could lose Gio Gonzalez to free agency, and Scherzer could lose a little something to the mid-30s aging curve, leaving the Nationals in need of an elite starter. And they will lose Ryan Madson and potentially other bullpen staples. The balance of star power on their roster will almost certainly shift significantly after the 2018 season, as payroll room allows them to pursue new stars (or old ones), and the front office decides exactly how to sustain success.

The state of their management could change dramatically, too. General Manager Mike Rizzo, the architect of their relevance, is under contract through Oct. 31 and has said multiple times that he will not approach Nationals ownership for an extension. Nationals ownership has proven multiple times that it does not go out of its way to give them. People within the industry believe Rizzo could get another job — if not a GM job — somewhere else, thanks to his resume and connections throughout the game, so he is not without leverage. But as next offseason brings the Nationals their greatest bout of roster uncertainty since this run began, not extending Rizzo could send them ricocheting into a new plan thrown together on the fly, perhaps sealing that window shut until a new regime gets its footing. Extending Rizzo would allow the Nationals to continue working in their current framework, one that has proven itself capable of sustaining success, and of providing annual World Series contenders — if not yet a winner.

Similarly, Dave Martinez’s first year as Nationals manager could also determine a great deal about their next few seasons. To keep up with the managerial market, the Nationals gave the rookie manager a three-year deal with a fourth-year option — a long contract by their conservative standards. While the deal was worth $2.8 million total, meaning cutting ties with Martinez would not be an expensive proposition, another failed search for a steady manager would cost the Nationals in more destructive ways. They have charged through three managers since 2013 — used three managers to win four division titles. If things fall apart this season, will they be in the market for their fifth manager since 2013? If things go well, but not well enough, is Martinez safe? On the other hand, if Martinez establishes himself as the kind of well-regarded manager many expect him to be, perhaps the Nationals will have found some long-term stability just in time for transition. Either way, Martinez’s first season has as many implications for his future as the organization’s.

All of these details, of course, pivot on the 2018 season. The Nationals are once again loaded with talent, and while Murphy will enter spring training needing time to rehab his surgically repaired knee, he and Harper will be back in the middle of the lineup along with revived Zimmerman and MVP candidate Rendon. They began rebuilding their bench with the bargain signing of Matt Adams, and might just enter spring training with the most stable bullpen they’ve ever had at that time of year. In other words, they’ve got a legitimate World Series shot once again. To fall short would be the norm, another example of baseball’s cruelty, of whatever they’ve been missing, a signal for an offseason filled with tweaking but not overhauling. But to win could change everything, the legacy of this first Nationals contender, the legacy of their general manager, and the long-term partnership of the two. So the Nationals welcome the new year knowing it brings with it a stark reality: While all years carry pivot potential, for the Nationals, 2018 could (and almost certainly will) change everything.

Read more Nationals and MLB coverage:

After roller-coaster season, Nationals reliever Sammy Solís wants to prove he’s reliable

A.J. Cole wants to be the Nationals’ fifth starter

Next season could be Wilmer Difo’s audition to be Nationals’ future second baseman