The young Mets that Dan Warthen now coaches sometimes ask about his playing career, and they have to pry details out of him. Just like them, Warthen was once a young hotshot, a high draft pick by the Montreal Expos with three good pitches at his command.

In those days, in the 1970s, there was not the same emphasis on pitch counts or innings limits. The game was not as specialized. Pitchers pitched until they could not get outs anymore. Warthen began as a reliever and worked into the rotation. Between starts, the Expos had him come back and pitch in relief, instead of throwing a bullpen session, to stay sharp. He was 22 and felt strong. He did not ask questions.

“You were making no money in the majors at that time,” Warthen said as he sat in a dugout recently, telling the story he does not tell often. “There was somebody to take your job all the time. You had no clout. You had no power. If they asked you to pitch, you went out there and pitched.’’

In his second career start, on a July night in Atlanta, Warthen pitched nine innings, struck out nine batters and gave up one unearned run. He threw 142 pitches, an enormous amount by today’s standards. Two days later, he threw 17 pitches in relief and walked three of the five batters he faced.

And right after that, Warthen sensed that his arm was not the same. And it never was again.

He had lost his velocity, the basic feel for his pitches. But he kept pitching, gutting his way through outings. He threw 134 pitches in his fourth career start. In another game, he threw 164 pitches in 10 1/3 innings. As an encore, he threw 130 pitches.

But whenever Warthen threw hard, he felt a gap in his elbow. He guessed he had torn his ulnar collateral ligament. But Dr. Frank Jobe had repaired Tommy John’s damaged ligament only a year before. The science was new, and Warthen did not have enough money to miss a year of baseball. He pitched in the majors for three more years, his arm a mess. And then he was done.

Now, four decades later, in his eighth year as the Mets’ pitching coach, Warthen is charged with the greatest task of his second career: nurturing and developing one of the best young pitching staffs in baseball. Of the four highly dynamic starters the Mets planned to use in their National League division series, three of them have had Tommy John surgery. It is Warthen’s job to protect them, to make sure what once happened to him does not happen to them.

“There’s an old expression,” said the 62-year-old Warthen, who has a professorial look about him thanks to his dark, thick-framed glasses. “Nobody cares how much you know until they know how much you care. They know that I care about them.”

Back in spring training this season, the Mets held a meeting to discuss how they would handle their pitchers this year. Coaches, scouts and front-office personnel attended. Their goal was to develop a plan to keep their young starters healthy and maximize their performance.

Matt Harvey was coming back from Tommy John surgery and needed his innings limited. Jacob deGrom, who has had Tommy John surgery, was entering his first full season in the majors. Noah Syndergaard and Steven Matz — he, too, has had Tommy John surgery — were close to being called up from the minor leagues, and Syndergaard, in particular, needed his innings monitored.

“It was a discussion about the whole staff, because anything we did to manage Matt’s innings was going to have a ripple effect on the other guys,” John Ricco, the assistant general manager, said of the spring training pitching summit. “It wasn’t like we could throw all those innings on one of the other young pitchers. That wouldn’t have made much sense.”

Warthen knew the pitchers better than anyone else in the Mets’ front office. He understood their makeup, their mechanics and their flaws. He tracked every pitch that was thrown and taught his staff new pitches or new ways to grip old ones.

One of the pitches he teaches is what the FanGraphs analytics website called the Dan Warthen slider, a pitch that is held deeper in the hand, runs harder and puts less stress on the elbow. It is a pitch that has been highly successful for deGrom and Harvey, among others.

“Every time he comes up with a plan, you trust him so much,’’ Syndergaard said. “You know it’s going to work.’’

Warthen can spot when Harvey’s leg kick gets too big, when deGrom’s front shoulder tilts, when Syndergaard’s foot mistakenly comes off the rubber. Then Warthen knows what to say to fix things. During tense moments in games, when he has to pay a visit to the mound, he may tell a joke to lighten the mood. Not many of them can be repeated for public consumption, his pitchers noted.

Warthen has been coaching for more than 30 years, has been with assorted major league teams, and has figured out his own way of doing things. At the ballpark, he requires the starting pitchers to watch one another’s bullpen sessions. He feels the interaction gets the pitchers to talk about their work on a deeper level. On occasion, Warthen will grab a postgame beer with his pitchers.

“Baseball is such a business, and sometimes you get so caught up in the business of things,” said Bobby Parnell, another Met who returned from Tommy John surgery this year. “To have somebody that can relate to you on a more personal level, it makes things more enjoyable and easier to come by.’’

About once a homestand this season, Warthen and manager Terry Collins met with general manager Sandy Alderson and reviewed where they stood with the pitching staff. Besides the number of innings pitched, the Mets were tracking the number of pitches per inning, their velocity and even the number of stressful innings. Warthen and Ricky Bones, the bullpen catcher who had Tommy John surgery as a pitcher, also evaluated pitchers with the naked eye test. Warthen was paying particularly close attention to his pitchers’ mental sharpness and mechanics.

“All the things that might be an indicator of fatigue,” Ricco said.

Everything was more or less going according to plan, Warthen said, when, in early September, Scott Boras, Harvey’s agent, created an uproar when he asserted that Harvey should be limited to 180 innings, which was around the total he threw in his last healthy season, in 2013.

During his recent interview, Warthen called the Boras incident “ludicrous,” arguing that the 180-innings total urged by Boras was only five to 10 innings fewer than the Mets had already planned for Harvey in the regular season. And because of the extra rest the Mets had periodically given Harvey as the season progressed, Warthen felt Harvey was strong enough to keep pitching beyond that number when the postseason arrived.

“How often do you get to go to the playoffs?” Warthen asked.

The Mets ultimately seemed to win out over Boras: After they lost a September game against the Yankees, in which Harvey was pulled early after five shutout innings, the pitcher requested that the Mets allow him to work regularly for the remainder of the season.

He finished with 189 1/3 innings in 29 starts. But he averaged just 96.5 pitches per outing and 14.8 pitches per inning, making him among the most efficient starters in baseball.

And before Harvey’s final start of the season, Warthen calculated that Harvey had also made 853 fewer throws this year — in starts and bullpen sessions combined — than in all of 2013.

In any case, it is now on to the postseason, where deGrom, Syndergaard and Harvey were set to pitch the first three games against the Los Angeles Dodgers. Meanwhile, Warthen said he held no ill will toward Boras, baseball’s best-known agent.

“If I were going to have an agent in today’s game, it’d probably be Scott,” Warthen said. He added, “He just wants to make sure his client stays healthy and pitches for a long time.”

After Warthen’s playing career fizzled, he settled down in Portland, Oregon, with his wife, Andrea. He learned as much as he could from his father, who was a stone mason, and started his own construction company. But after about a year and a half, he decided he missed baseball too much and became a coach.

That was 34 years ago. In all the time since, Warthen has developed a list of three reminders he gives his starters when they’re walking together, just before the game starts. Get the first out of every inning and throw first-pitch strikes. “Most of all,” he tells them, “have fun.”

And as far as throwing way too many pitches, do not worry: Warthen has their back.