After making the Nationals respectable in two seasons, General Manager Mike Rizzo said the team was a player or two away from contention. But it seems ownership has not opened the purse strings to sign any significant players. (Toni L. Sandys/The Washington Post)

The Washington Nationals never really seem to learn. Or, rather, the Lerners don’t. As soon as you think they start to get it, they backslide again.

When are the Nats going to be allowed to be good? When will they get to build a winner with a roster that has a sensible margin of safety, rather than constructing a team that can succeed only in a best-case world?

When are they going to stop trying to build a suspension bridge with the minimum amount of steel and then, as happened in 2008 and ’09, act shocked if it collapses? After one 80-81 third-place year, have they forgotten the pain?

It’s happening again. All the signs are there. The Nats’ baseball people lay out clearly what they want to achieve in the offseason. None of it is terribly difficult. But there is risk and expense. Then, as the offseason unfolds, nothing happens.

Was Jayson Werth just the exception that proves the rule? Even his signing only nudged the Nats’ 2011 payroll over its ’05 level, when the team was an MLB chattel. Is what we’re seeing, again, really the distressing norm?

“We’re busy. We’re trying to be aggressive but broad-minded, we’re working behind the scenes,” General Manager Mike Rizzo said on Wednesday, adding that the Nats were working on “bench options.” Bench options? Pine or oak?

If you want to know why it’s almost Christmas and the Nats haven’t signed Mark Buehrle, Roy Oswalt or Edwin Jackson, why they haven’t bid on Yu Darvish or Yoenis Cespedes, why they haven’t been within a zillion miles of C.J. Wilson, Jose Reyes or Prince Fielder, and especially why they haven’t made a prospects-for-a-star trade such as the Reds for ace Mat Latos, it’s probably because ownership is tensing up, tightening the leash again.

It’s probably because real-estate gurus are giving the baseball lifers their opinion again on the value of ballplayers and the wisdom of deals.

Give the Lerners some credit: They do learn, but only glacially and always with setbacks. It’s one thing to sign amateur draft picks “over slot” in defiance of unwritten rules among owners. Those players are bargains even at the prices the Nats paid. The Lerners saw it. But when your GM says in public what you need in the offseason, that’s a vital component, too.

This is a particularly ugly moment for the franchise to appear paralyzed because at some point next year, the Nats will have a new deal with MASN that doubles or even triples their current rights fee. Now it’s between $25 million and $30 million. Soon it’ll be at least $30 million higher. The industry knows this elephant-in-the-room windfall is coming.

How much fresh revenue is that? It would soak up what the Marlins just spent in long-term money to sign Buehrle and Reyes. And the Nats’ payroll, currently headed to just the $70 millions (maybe), would be low enough that you could try to trade for a Latos or almost any name. Just saying.

So what’s up with the Nats? Three months ago, Rizzo came right out and said, “I think we’re an outfield bat away and a starting pitcher away from really being a contender in the division.” Three weeks ago, before the winter meetings, he said the same to me.

Now, half the winter merchandise is off the shelves, Rizzo is empty-handed, and the Nats could end up with one of game’s worst offseasons.

Other teams act when fresh cash is coming — either because of a new ballpark, such as the Marlins, or a new TV deal, which helped the Angels and Rangers justify their current big spending on Albert Pujols and Darvish, respectively.

Three weeks ago, the Nats had so many possibilities for improvement in so many areas and through so many different methods. But until you make your first moves, you can’t get to the rest of the puzzle.

Instead, they’ve done nothing except sign washed-up center fielder Mike Cameron, 39, to a minor league deal. Was that a flare from Rizzo? Venezuela rescued Wilson Ramos in two days; who’ll free the Nats’ GM?

In baseball, no pitfall is more common than becoming infatuated with your own young, unproven, inexpensive players. For example, you look at Ross Detwiler, Brad Peacock and Tommy Milone and figure one of them most likely will become a 100-game winner. Sorry, tilt! Not how it works. They’re nice prospects. But odds are that none ever has a 15-win season. Buehrle and Oswalt already have won 161 and 159 games, respectively — and each may win 50 more.

The other classic snare for owners is to delude themselves that spending huge sums will be much easier — so much “clearer” — in some vague future year when the free agent grass is greener. Most years, the Nats blundered both ways. They’re halfway to doing it again.

When your GM, in two years, has taken your pitching staff from the 28th-best ERA in baseball (5.00) to seventh-best (3.58), and he says, “We need a top-of-the-rotation starter to go with Strasburg and Zimmermann,” the only correct answer is, “Thank you for turning our hideous pitching into a strength so quickly — all pre-Strasburg — while also developing such a promising pipeline. Looks good to us, but if you think we need even more pitching, what do we know? Go do it.”

However, here’s what’s worse that not opening the checkbook for free agents — and it’s what I suspect is happening now. If your baseball people say: “We finally have the prospects to trade for a key piece. We’ll have to give up lots of promising cheap labor and we’ll have to pay the new star immediately. But it’s the right move,” then the owner should say, “Yes!”

A timely “yes,” a strong predisposition to trust the recommendations of top executives, is exactly what the Lerners have never provided the Nats. It remains their flaw. It’s always the same: Start from zero and build an ironclad logical case, full of slides and graphics, so Ted will cut the check. Many who’ve worked for the Nats say the same thing, in the same words: Their toughest negotiation isn’t with agent Scott Boras but with Ted Lerner.

Perhaps Nationals fans should apply a similarly high threshold of proof before they sign their checks to the team. Make the club demonstrate its case. Enact the winter strategy they so clearly laid out. And, with tens of millions of new TV dollars a year about to rush through the front door, it’s a plan the team can obviously afford — but, so far, has done absolutely nothing to execute.