To understand, at least in part, why the New York Mets’ rotation is falling apart from Tough Guy Syndrome while the Washington Nationals continue to handle their pitchers with kid gloves, you need to grasp the personalities and backgrounds of the teams’ general managers, Sandy Alderson and Mike Rizzo.

First, the facts on the ground: Mets ex-ace Matt Harvey will have season-ending surgery for thoracic outlet syndrome, which — among other unpleasantness — requires the removal of a rib. Nats Manager Dusty Baker, ever helpful, recalled a hurler he once knew who had TOS, “but they took out the rib on the wrong side.”

After the way the Mets have manhandled Harvey, anything could happen. In 2014, after elbow ligament replacement surgery, he pitched 0 innings. In 2015, that number exploded to 238⅔ innings, including spring training, blowing away any total for a man returning from a “0” season after having Tommy John surgery, an operation with 42 years of recovery-protocol data available.

[Matt Harvey is out for the remainder of the season]

With a month left in the regular season, Harvey and agent Scott Boras, who also represents Stephen Strasburg, protested that they thought or had been told that Harvey would be shut down as Strasburg had been in 2012. Alderson said no such understanding existed, and with huge pressure from New York media and fans, Harvey flipped positions and pitched ruggedly until the end of the World Series.

Scott Boras, left, and Nationals GM Mike Rizzo, right, flank Nationals ace Stephen Strasburg as a news conference announcing his seven-year, $175 million extension. Strasburg decided to stay in Washington, in part, because of the cautious way the Nationals handle his workload. (Jonathan Newton/The Washington Post)

On Friday night, Noah Syndergaard, who acknowledged he had been pitching through the pain of bone spurs, left his start against the Nats after 79 pitches “because of arm fatigue — not elbow related,” the Mets said. Thor’s velocity had dropped from 100 mph in the second inning to 93. Jayson Werth said that “the way they came out [of his hand] just wasn’t normal.”

Young star lefty Steven Matz, scheduled to face the Nats on Sunday, is also pitching through bone spur elbow pain. The Mets don’t sugarcoat it. Their public position on Syndergaard and Matz has been: Tough it out. When you can’t, let us know.

Weeks ago Harvey noted some loss of feeling in his fingers, a symptom of TOS. He skipped a start but kept pitching. On Friday, the New York Daily News reported that, while Alderson believed TOS surgery was inevitable, the GM thought that Harvey also could have had a nerve block injection and continued to pitch this season.

[Mets fans rally to support struggling Matt Harvey]

If you are a young Mets pitcher, what would you have to say to set off the Mets’ alarm bells? What about: From my fingers to my shoulder, I feel like I am being eaten by fire ants. Oh, we have nice nerve block for that; you won’t even know you have an arm.

In ironic contrast, Strasburg — sometimes accused of being a hothouse orchid — continued to respond to frequent pruning and assiduous watering with a 3-1 win Friday over New York, pushing the Nationals’ NL East lead back to four games.

1 of 52 Full Screen Autoplay Close Skip Ad × 2016 Nationals: Stephen Strasburg notches No. 12 View Photos Right-hander’s 12-0 start is the best in the National League since 1912. Caption He’ll be the Game 1 starter Friday against the Dodgers. Nationals 10, Marlins 7 On the final day of the regular season, Max Scherzer won his 20th game. Afterward, he hugged his catcher, Pedro Severino. Toni L. Sandys/The Washington Post Buy Photo Wait 1 second to continue.

Since June 23, 2015, the Nats are 26-3 in Strasburg’s starts. This year, he’s 12-0. Tender-loving-care is in danger of getting a good name. Last month, the Nats sent Strasburg to the disabled list at the first sign of the upper-back pain that hurt him twice last season. He came off the DL on July 3 and pitched ­10 2/3 consecutive no-hit innings.

Are the Nats and Strasburg wimps? Or smart adherents to best medical practices? Data points for the debate seldom stop arriving. The Nats now say that Strasburg will not pitch in the All-Star Game on Tuesday in his home town of San Diego, even though he probably would have been named the starter and would have had three days’ rest.

The decision was basically Strasburg’s. As Baker said, “How can you tell a grown man he can’t pitch in the All-Star Game?” But Rizzo, the architect of the Strasburg shutdown in 2012, again said that Strasburg’s long-term production was a priority and that it was a “mutual decision.”

“He had the same back issues twice last year . . . ended up on the DL. . . . Now [same thing] again. We felt [this] was in the best interests,” Rizzo said.

How can two teams be run so differently? In part it’s a function of ownerships and markets. Nationals owner Ted Lerner is extremely patient, a long-term builder, rare in a 90-year-old. The Mets, in the most baseball-crazy market on earth, can’t afford to be wired that way and still compete against the Yankees’ unique brand and deeper pockets.

Alderson and Rizzo are extremes within their professions, yet both match their town’s baseball temperaments as well as the marching orders they have been given.

Alderson is the son of an Air Force pilot who flew missions in World War II, Korea and Vietnam. Alderson, a graduate of Falls Church High, Dartmouth and Harvard Law, self-identifies as a Marine in Vietnam. When Baker played for Alderson in Oakland, Dusty asked about the picture of a man in uniform on Alderson’s desk. “Who’s that?” Said Alderson: “Me.” He and Baker, also an ex-Marine, hit it off.

[Max Scherzer replaces Stephen Strasburg as all-star]

As a top executive with three teams and a key man in the commissioner’s office for many years, Alderson fulfilled tough tasks for owners with limited budgets and dedicated himself to the health of the game. In every role, he has been a company man and proud of it.

Alderson never played pro ball, and his standard of toughness for players can seem like a battlefield code of honor rather than an athlete’s.

Rizzo was a minor league player, drafted 554th in 1982. The son of a lifelong scout, he has deep regard for the gifts of his players, and though he’s an Illinois grad, he sees himself as a scout with 300,000 miles on his car. And for someone in management, Rizzo may come closer to identifying with labor than any GM.

Experience tells him that management will drive players past the point of productive common sense and sometimes even abuse them as if they were interchangeable machine parts.

Rizzo identifies intensely with players, many of whom he scouted, signed or acquired in trades. They’re almost like nephews. In some cases, he may stick with them too long and go beyond industry norms to protect them before or after injuries. And when his scout’s eyes tell him somebody’s not yet washed up, no power can sway him.

The Mets, doing it Alderson’s way, have an NL pennant to show for their 2015 forced march. The price they will pay is TBD, in baseball parlance. Toughness can be expensive. The Nats, with Rizzo, have the second-most wins in MLB in the past five years. But they have never won a postseason series and have been accused, publicly by Tim Hudson in 2014, of not being tough enough to win it all.

[Stephen Strasburg improves to 12-0]

Yet this past week, the Nats had so many healthy top-level starters that, to find room, young Joe Ross was put on the 15-day DL with a minor “injury” so that he would be fresh for September and October — without surpassing wise innings limits.

The best case for the Mets is that all, or most, of their pitching mega-talents survive these tough times and have the careers that their talents and work deserve. And eventually get paid properly, too.

The worst case is that many of the members of the Mets’ rotation from 2015, plus Zack Wheeler, who had a setback recently in his rehab from Tommy John surgery, never live out the careers — the stellar seasons, lifelong memories and, yes, the pay days — they might have had.

The Nats put the arms of Strasburg and Jordan Zimmerman, now a Tiger, ahead of short-term considerations. Those two are guaranteed to make more than $340 million in their careers. All five of the current young Mets starters combined, including Wheeler, are assured 1/30th of that. Is that exploitation? Do the Mets want to “win now” too much? Or the Nats too little?

That debate isn’t going away. But tons of data is on display — right here, right now. And the preponderance of it is pointing in the same direction.

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