Nationals pitcher Jordan Zimmermann might be headed for another organization at the end of the season. Part of the reason could be the Nats’ reluctance to bet on a once-rebuilt elbow. (John McDonnell/The Washington Post)

The life expectancy of a “second elbow” after Tommy John surgery is thought by some in baseball to be about eight years. One of the teams that believes it, not as dogma but as an important rule of thumb, is the Washington Nationals.

And that explains a lot. Like why Max Scherzer arrived. Why Jordan Zimmermann almost certainly will leave after the 2015 season. And why, hold on, Stephen Strasburg is highly likely to depart D.C. after the 2016 season as well.

First, we need context. The Nationals believe sports medicine is a serious competitive advantage in baseball. They love scouting and talk about it constantly. But they are just as serious about their best-practices medical philosophies. How seriously do they take them? How far will they go to follow them? You know. They shut down Strasburg for the 2012 playoffs with the whole world hissing.

Most such protocols and theories are proprietary. But the Nats can’t hide their views on elbow ligament replacement surgery because it has clearly impacted or determined so many of their most important personnel moves. In doing this, we infer. But we’re also right.

The Nats absolutely love Surgery No. 1 because they — and others — think it has about a 90 percent success rate. They will draft pitchers in the first round who are almost certain to need it, like Lucas Giolito in 2012 and Erick Fedde in 2014, that other teams are afraid to touch. It has paid off big. Both blew out almost immediately. Giolito, back throwing 100 mph, is the top pitching prospect in baseball, and Fedde started throwing again here in spring training.

Stephen Strasburg, here using a rubber band to warm up his arm in February, could be six years removed from elbow ligament replacement surgery when it comes time for the Nationals to commit to him again. (Toni L. Sandys/The Washington Post)

[ Two Tommy John surgeries too much of a good thing? ]

But the Nats hate and fear Surgery No. 2 because they — and others — think it has an awful chance of saving a career — perhaps 20 percent. Just last season, the Braves were devastated when stars Kris Medlen and Brandon Beachy required a second elbow ligament replacement surgery. Atlanta gave up, releasing them both.

With this as background, consider Scherzer. He has never had the surgery. So if needed, a second elbow awaits him someday. That thought helps owners and general managers sleep at night. It might be a false sense of security. But when they hand out $210 million guaranteed, even billionaires need security blankets.

Also, fear of “TJS2” is part of why Zimmermann is leaving after 2015. He’s starting his sixth season of pitching with his “new” elbow. There are many factors in the inability of the Nats and Zimmermann to reach a contract extension.

“I don’t know if that is part of it,” Zimmermann said of his TJ history. He added, “It doesn’t look good,” and he won’t negotiate during the season. The whole sport can translate that: He’s gone. “You never know, but it’s been awesome here,” he said.

The Nats have made a satisfactory extension offer to Zimmermann, probably similar to their $107 million offer to Ian Desmond. If you include Zimmermann’s current $16.5 million for 2015, he’s likely in the same $125 million ballpark as the total-dollar deals to Jayson Werth and Ryan Zimmerman.

That’s a guesstimate number the Nats seem to like or, perhaps, where they get stuck. It’s certainly not a “we just gotta have you” offer. If Zimmermann has a monster year and gets a near-Scherzer contract, he might make $200 million, including 2015 bucks. So don’t blame him for not grabbing money that none of us can imagine.

But if he has a year as bad as Justin Masterson did in 2014, he could cost himself the $100 million-plus that has been on the table. So no stress. Just a game, right?

The surprise — and disappointment for Nats fans — is that the Zimmermann Farewell Scenario is playing out again right now, letter for letter, with Strasburg. As was pointed out here a year ago in the cases of Zimmermann and Desmond, teams that truly want to get big extensions accomplished do it two seasons before the player’s “walk” date. “Everybody understands that — two years. That’s when [the risk-reward for] security-versus-injury are about equal for both sides,” says a player who has a nine-figure contract. The Nats and Strasburg seem to be nowhere.

In part, that might be because Strasburg’s agent, Scott Boras, has a history of avoiding extensions, believing they shortchange clients. But the Nats are also reluctant because 2016 will be Strasburg’s sixth season with his “second elbow,” exactly the same timetable as Zimmermann.

Obviously, no two pitchers — or patients — are identical. They might not even be similar. But at least in the Nats’ world, that “eight years” guess carries weight.

Who would logically slot as a Strasburg replacement? The No. 1 pitching prospect in the minors: Giolito, with less than two years’ mileage on his new elbow.

If next year at this time Strasburg is in the same position as Zimmermann now, we’ll know that elbow ligaments and medical theory mean more to the Lerners than Boras doing his best, “Look deep into my eyes.”

Part of following a team is gradually understanding its methods in depth. Don’t be fooled by Scherzer’s $210 million deal. The Lerners are not sentimental or extravagant. That deal maximizes 2015 outcomes but also fits in context with all the contracts that soon will come off their books, perhaps $60 million after this year.

One of baseball’s menacing trends is the glut of monumentally bad long-term contracts to pitchers 30 or older. Scherzer’s could be one; but at least he comes with that spare elbow. If a D.C. star already has had elbow surgery, the Nats know how to count to “eight,” even if the guy might cross them up and win 20 at age 40.

In fact, that longevity countdown might be a pivotal factor two years in a row with Zimmermann and Strasburg. You would almost think it was a business.

For more by Thomas Boswell, visit washingtonpost.com/boswell.