Dan Haren and Denard Span may or may not work out well for the Washington Nationals. But these two decisive, strike-first acquisitions are exactly the proper way to run a big league baseball team. This is the kind of multi-track planning, we-do-it-our-way evaluating and rapid decision-making that deserves to win. Will it? Wait and see.

In building an outstanding baseball team, history has proved that lots of theories can work. What matters most isn’t exactly what you believe; it’s that you act on what you believe with conviction and consistency. Sooner or later, the team that knows its own mind usually ends up in the World Series.

That self-assurance in taking control of events rather than waiting for them to control you is a core part of why the Nats have risen from 103 losses to 98 wins in just three years. And it’s a reason that Haren, one of baseball’s best pitchers of the past eight years, just grabbed a $13 million, one-year deal Tuesday to join a Nats pennant push. Remember when the Nats had to give an extra year, perhaps two, to get free agent Jayson Werth to sign?

“The sky is the limit for this team,” Haren told The Post’s Adam Kilgore.

After a career of remarkable durability, Haren made his first trip to the disabled list last season.

The Post Sports Live crew discusses the Nationals’ signing of free agent starting pitcher Dan Haren. (The Washington Post)

“I’m confident I’ll hold up my end,” he said. “The deciding factor . . . was winning. I don’t think there’s a team better positioned to win now. . . . It didn’t take me long to decide.”

Whether the Nats are shutting down Stephen Strasburg or intensely courting Adam LaRoche (on their terms) while making moves that render his decision tangential, they do things their way. And GM Mike Rizzo and Manager Davey Johnson don’t much care what others think. Span asked in a tweet, “What’s Natitude?” It’s trading for you, buddy, when plenty of others wouldn’t, then putting 13 million chips on Haren-to-win.

That swaggering confidence is why the Nats almost finished their offseason work before the winter meetings, the supposed ignition of the hot stove league, even reached their midpoint Tuesday. While other teams still have a finger in the wind or hope Zack Greinke loves ’em, the Nats have only one lefty bullpen spot to fill. If their own free agent LaRoche signs for two years, that is great. If not, the Nats have first basemen aplenty, with Michael Morse, Tyler Moore and more in the minors.

What will the Nats’ winter hold? We can stop asking. Except for LaRoche’s decision on himself, they are basically done, and winter’s still 17 days away.

When it comes to Haren and Span, what do the Nats believe so firmly? And are they more likely right or wrong?

The Nats think Haren’s back and hip, which forced him to miss three starts in a 12-13 season, are minor issues, if that. “I feel great,” said Haren, who came back to post a 3.65 ERA in 13 starts after returning from the DL. Reports say the Red Sox didn’t like the look of the medicals on Haren’s hip. Haren says he’s had that same problem for many years, and it’s irrelevant. We’ll see who did better homework.

Age 32, with 119 wins and almost 1,900 innings on the odometer, is a risk in itself. You can make a list of pitchers comparable to Haren who were good to exceptional at that age, from Jim Bunning (19-8) to Bill Gullickson (20-9) to Kevin Appier (15-11). And there’s an equal list of those who were fading fast at that age, such as Josh Beckett , who bombed in Boston last season.

Explore the Nationals’ run to their first NL East title.

The Nats think Span, despite no power and speed that translated into just 17 steals last season, is exactly the ballhawk they need in center field — letting Bryce Harper move to a corner spot.

And Span’s a twofer, giving them the patient career .353 on-base percentage lefty-hitting leadoff man who will let them drop Werth to a better RBI spot. It’s not an obvious decision. That’s why they got Span for just one prospect, albeit a good one, and must pay him just $11.25 million the next two years.

Why was Span tradeable for the Twins? Why didn’t the Angels pick up a $15.5 million club option to keep Haren? What do these teams know? Have the Nats outsmarted themselves in one or both moves? Could be.

But the Nats now have a five-deep rotation, with Haren near the end (gasp) of the line, which, if heathy, could be stupid good. The lineup, with Werth no longer at the top and Harper in the middle, could be classic, including five players with speed on the bases and six spots with power.

The Nats say they are a 65-35 “scouting over advanced stats” operation. But the geeks should rave about adding Haren and Span, whose levels in Wins Above Replacement (WAR) in any multi-year period obliterate the players they may replace in Edwin Jackson and LaRoche.

It’s rare to see a team know its short- and long-term plans and then find a way to pursue both simultaneously. The Nats want to have a shot at the World Series next year. With bullpen tweaks and a healthy Haren, that looks perfectly plausible.

But the Nats didn’t want to tie up so much payroll that they couldn’t pursue long-term contracts, at various times, for their best young players.

Finally, the Nats wanted to keep the path clear for their best developing hitters. With Morse a free agent after ’13 and an option on Span for 2015, the Nats have kept those options open, too.

Two weeks ago, the Nats name was connected to expensive free agents such as Greinke, Michael Bourn and B.J. Upton with an undercurrent that the Nats might sign a Scott Boras client or at least help him make a market.

All wrong.

Is the Nats front office really this red hot? Are they finding comparable, or even better, values at far lower price points than other teams? Are they building a 2013 roster that makes Haren giddy while also protecting a “window” of at least four years and maybe more?

Perhaps this is all just a little too much to swallow in one gulp for a franchise that, at this time a year ago, hadn’t had a winning season in D.C.

But you could definitely get used to it.

For previous columns by Thomas Boswell, visit