Of course, such a Rendon deal, impacted by Nolan Arenado’s seven-year, $234 million extension this past week, might be for six years, while the Phillies are tied to Harper for 13. The size of potential long-term problems is very different.

In fact, if the Nats had guessed the future of the Harper market perfectly, they might have played their cards the same way: by moving on from Harper late last year, never circling back aggressively in recent weeks and settling for a solid roster that is under the luxury-tax ceiling and has room to sew up Rendon for years.

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But the abstract world of second-guessing with perfect hindsight is a magnificently horrid thing. Could the Nats have stayed in the Harper picture all winter and, if they got him, let Rendon leave after this season, with Carter Kieboom as the heir to third base? We will never know. And it will take several years — maybe many — before we truly can analyze the impact — and the spin — of the Harper haul on both teams.

But one thing is certain. Getting Rendon, who is in his walk year, extended deep into the next decade is the Nats’ Job 1, 2 and 3. Harper never had the leverage with the Nats that Rendon does now.

Many people, including me, are sick of hearing about contract negotiations when spring training has started. Part of the irritation is that the pro sports ostentation meter has blown right off the top of my chart. Also, much of the chatter is speculation with an agenda. But the Arenado-Rendon connection — and the general framework for a Rendon-Nats extension — has a specific answer.

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Arenado’s deal probably will put a few million more dollars in Rendon’s pocket. But it also should make it easier for the Nats, Rendon and agent Scott Boras to come to terms on an extension if that’s what they all want.

Cut to the chase: What does Arenado’s deal, which takes him through his age-35 season, tell us? Answer: Rendon probably deserves a six-year extension for the 2020 to 2025 seasons of about $144 million. Because supply and demand just tilted in Rendon’s favor, he may get more — like $25.4 million?

The Nats can afford it, though it’s probably a bump up from what they expected just days ago. And Rendon has a chance to negotiate at an excellent moment, coming off back-to-back stellar seasons, in perfect health and with Arenado as a “comparable.” Get it done by Opening Day? Maybe.

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What is the reasoning behind these numbers?

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Several weeks ago, Arenado and Rendon, both in their walk year before free agency, signed deals with their teams — for $26 million and $18.8 million, respectively — to avoid arbitration. In both cases, the players and their agents negotiated contracts that they considered fair. Because both are stellar third baseman in the National League, Rendon negotiated in full awareness of Arenado.

The career arcs of the two players are almost identical, except Arenado is 27 and Rendon 28. Both have been stars for the past five years.

Why would Rendon accept a 2019 contract for 72 percent of Arenado’s deal?

Part of the reason — a statistical accident but interesting — is that Rendon’s Wins Above Replacement over the past five years (21.1 WAR) are 72 percent of Arenado’s WAR of 29.3 over the same period, as calculated by Baseball Reference.

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A big part of the gap is that Arenado, helped by playing in mile-high Coors Field, has far more hardware, including six Gold Gloves, four all-star selections, three home run titles (in the past four years) and two RBI crowns. He has finished eighth, fifth, fourth and third in NL MVP voting in the past four years. Rendon has led the NL once in runs and once in doubles and has finished fifth, sixth and 11th for MVP honors.

What matters, I assume, is that Rendon and Arenado have been negotiating deals throughout their arbitration years, and the pattern has been similar: In 2018, Rendon made 69 percent as much as Arenado.

Here we go. Watch how easy it is to be an agent. (Where’s my 3 percent?)

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Arenado’s extension has an average annual value of $33.4 million. If Rendon made 72 percent as much, that would be close to $24 million. Because Rendon is older, he would get a six-year extension through age 35, not seven years. And $24 million times six seasons is $144 million. Done deal! (You’re welcome.)

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Or, if you want to gussy up the numbers as some do, you can include their new 2019 contracts and say that Arenado now has a $260 million deal for eight years and Rendon’s would be $162.8 million for seven years.

Of course, that six-year, $144 million number is a ballpark figure. But it’s a number with which the Nats — and their other top players — should feel comfortable. Patrick Corbin just got $140 million for six years. Stephen Strasburg is on a seven-year, $175 million contract, and Max Scherzer is in a seven-year, $210 million pact. Ryan Zimmerman is finishing a six-year, $100 million extension.

For reference, last March, Jose Altuve, the 2017 AL MVP, signed a five-year extension with Houston for $151 million through age 34. Also last year, J.D. Martinez, coming off a 45-homer year, signed a five-year, $110 million free agent deal and helped the Boston Red Sox win the World Series. Should Rendon be more like $120 million for five years? Possibly. Jeez, let’s leave something for them to fuss over.

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If the Nats can lock down Rendon with an extension, they may be getting something of a bargain. In his career, Rendon has hit almost identically at home and away with an .826 on-base-plus-slugging percentage on the road vs. .833 at home. Arenado — feel free to be shocked — has a career OPS of just .787 on the road but destroys pitchers in the light air of Colorado with a .984 career OPS.

Is it possible that Rendon is as good of a hitter as Arenado if only they played in the same park? It’s conceivable. But few get paid based on “if only.”

As for defense, Rendon is special — in the same class as a young Zimmerman. Arenado is otherworldly — in the same class as Brooks Robinson.

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Some deals just don’t seem meant to be. Harper and the Nats dealt with each other respectfully. But there was never a moment when either Harper or the Nats did anything that said, “We have to get this done.”

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But some deals seem meant to be. About 10 days ago, while shopping at Whole Foods in West Palm Beach, Fla., at spring training, I spotted Rendon pushing his cart through the aisles alone, dressed in jeans, T-shirt and sneakers — neat, unobtrusive. No one spoke to him as he eventually meandered through the checkout line. I didn’t bother him, either.