Ever since the Washington Nationals traded for all-star lefty Gio Gonzalez, fans have counted the days until Sunday, when pitchers and catchers report to spring training. Since Manager Davey Johnson said Bryce Harper might earn the right field job on opening day, they’ve scribbled lineups with Jayson Werth in center. Since the Nats spent $11 million for Edwin Jackson to get the pitching depth that often defines contenders, they’ve realized: It’s different this time.

This sense of infernally, eternally delayed baseball gratification, a wait that’s annoyed generations of Washington fans, including the Lerner family, now seems to be coming to an end. Finally, there’s a season that sends out a universal tingle. After signing Jackson, General Manager Mike Rizzo told me, “I have some phone calls to make.” To Johnson, he said: “[Forget] ‘potential.’ Let’s win some games.” To players, his message was, “The window is open.”

Every iota of the anticipation, excitement and trepidation that surround the Nats is totally warranted. One of baseball’s most promising but least battle-tested teams faces an appointment with its destiny. For the next five seasons, at the least, while Stephen Strasburg and most of the club’s other key players remain under team control, we will see its fate unfold.

What will this era produce — trips to the playoffs or World Series? Or, instead, what will it fail to create? We’re about to find out.

Sometimes, such glorious windows of opportunity crash down on the fingers of gifted but unproven young teams. Such sagas can turn sad in any sport. The Capitals are now in the fifth season of what was seen as an Ovechkin-Backstrom-Semin-Green era that would provide multiple trips to the Stanley Cup finals. That may yet happen. But the Caps already serve as an object lesson to the Nats. “Main chances” don’t come often. Success is never just a matter of time. In the end, time always runs out.

On Monday’s first workout in Viera, Fla., the Nats’ clock starts ticking.

What is certain already is that the Nats are one of the best stories in the sport. The Washington roster is so young, or else under long-term contract, that the Nats can already name an entire 2013 team. Assuming a contract extension for Ryan Zimmerman and normal development by minor leaguers, the Nats also know almost every key player for ’14 and ’15. If anything, they may have to find room for four elite, far-over-slot draft picks taken last June, a spending stunt that is now forbidden by baseball.

Strasburg, Gonzalez, Drew Storen, Wilson Ramos, Danny Espinosa, Harper, Anthony Rendon, Henry Rodriguez and others, are all under team control through 2016 at least. That’s a five-year map of the future.

This level of roster stability, providing a chance to grow up together, almost never happens in the flux of modern baseball. But the Nats are doing it now. Only one free agent (Werth) is signed past this season. Few teams are so close to being entirely home grown. Trades, such as those that netted Ramos, Michael Morse and Gonzalez, are as old-fashioned as it gets.

Because the Nats have structured the future so clearly, and haven’t even hit an $85 million payroll yet, many counsel patience. Some think the Nats should regard themselves as being “a year away.” That’s because Strasburg will be limited to 160 innings. Harper, at 19, is unlikely to be a force. And the Nats, with the National League East’s lowest payroll, can sign a fine center fielder next winter.

Don’t buy this line of argument. The Nats are young, but in the game’s most important element — pitching — they are not raw at all. Gonzalez and Jordan Zimmermann had the 10th-best ERAs in the American League and National League last season. That’s not potential; it’s proof. Jackson and John Lannan have been credible, durable starters for four straight years. Strasburg, 24 in July, has the most dominant stats through his first 17 career starts since Dwight Gooden in 1984.

The bullpen, one of the best last year, won’t contain a single rookie and is anchored by established young power arms. As recently as mid-2010, the Nats would have begged Lannan, Chien-Ming Wang, Ross Detwiler and Tom Gorzelanny to be in their rotation. Now, one will be a starter, two may be in the pen and one figures to disappear.

How much does pitching really matter? For reference, the Nats were fifth in the National League in home-park-adjusted ERA last year. Now, getting perhaps 65 starts from Gonzalez and Jackson, plus about 59 starts from Strasburg and Zimmermann (vs. only 31 in ’11), they ought to improve.

Since ’96, NL teams that finish fifth, fourth, third and second in park-adjusted ERA have won an average of 86, 88, 88 and 90 games. With average health, that’s where the Nats probably sit — an 86-to-90-win pitching-based team with a rangy infield defense but a mediocre offense, despite a healthy Zimmerman and Adam LaRoche at the corners.

That sounds entertaining, especially compared to all previous D.C. teams going back to the 1930s. But what does being a good team, but far from a great one, actually get you these days?

Maybe a lot. In the last dozen seasons, seven World Series winners have averaged only 89.6 wins in the regular season. Three additional teams reached the World Series with an average of 89.7 wins. Call it postseason parity or call it a fluky October format built for cheap thrills and TV ratings more than a meritocracy. But it definitely adds fun for the fans of teams at the 85-to-90-win level, where the Nationals will probably find themselves either this season or very soon. If the playoffs are expanded to 10 teams for 2012, which seems likely, the hurdle for joining the playoff party drops with (according to history) 90 wins a lock, 89 a near certainty and decent odds down to 87.

This isn’t a playoff prediction for this year, or any other season. It’s an attempt to provide context for enjoying, or agonizing with, an 80-81 team that’s rapidly become relevant. The Nats have national buzz with their farm system ranked No. 1 recently by Baseball America and several “contender” picks from gurus. How deliciously disorienting to a city just seven years removed from a 33-season hiatus from the big leagues.

For weeks, friends and even strangers have asked me, in essence, “Is it safe?” to start investing allegiance, rather than passing interest, in the Nats.

It’s never safe. It’s baseball. But it’s time. That window is finally open. A new Nationals era, joyful or otherwise, begins this weekend.

For Thomas Boswell’s previous columns, go to washingtonpost.com/boswell.