With Jonathan Papelbon, you’re in for a dime, in for a dollar. The Washington Nationals have decided that they are in. All in. They have doubled down on their bet on Papelbon at the trade deadline last year. He’s not just still on the team after choking Bryce Harper. He’s also entrenched as its closer and maybe a team leader and tone-setter, too.

On Friday, Papelbon apologized to Planet Earth, including his teammates and Nats fans, for his infamous fight with Harper. “I was in the wrong,” said Papelbon, who offered to spend “all day” talking until the last question was answered but then vowed he would retire the subject for the year.

Then, by the next day, he was full-blown Pap again. Loud and large, he was at the center of the room, picking the team’s music play list, including the country song “Shut Me Up.” Key lyrics: “I’m the siren you can’t unplug. . . . The only switch that I got is ‘on.’ . . . You can’t cover up the truth with duct tape.”

Tell us how you really feel.

Already, Jonathan Papelbon, left, has influenced the more laid-back Gio Gonzalez. (John McDonnell/The Washington Post)

Don’t worry, he will. Later, he walked the Nats’ complex in a cut-off muscle T-shirt with arrows pointing to big biceps covered in jagged tattoos. The shirt said: “Obama Can’t Ban These Guns.” Pap wanted to wear that shirt to the “apology press conference,” but he was talked out of it.

If the Nationals were an accounting firm or any generic American business, this guy would be a contagious and damaging disease. But in pro sports, you can’t be so sure. Baseball’s not that simple. Papelbon could easily prove to be a clubhouse cancer. At 35, he could even be washed up. But on a team that new Manager Dusty Baker says needs to have more fun, as it did in 2012, and rediscover its swagger, it’s conceivable that Papelbon could also be part of a cure.

What’s certain is that the Nats’ gamble to keep Papelbon — and view him as a core team piece and tone-setter — is going to be one of the best or worst ideas a contending team has made in years.

All winter, I thought keeping Papelbon would be a disaster. He had provoked the Harper fight not because he cared whether Harper had run out a popup but because he didn’t like the 22-year-old MVP’s quotes about him after a game when Papelbon threw at Manny Machado’s head twice. Trade him, even release him.

Now, after seeing Papelbon in the mix here, it doesn’t seem so crazy. His locker is next to jovial Gio Gonzalez, a pairing of blithe spirit and Metallica. On Saturday, Pap, a conditioning freak who often wears a “Train to Reign” shirt, was agitating the laid-back Gonzalez about his workouts and his arrival time at the ballpark. When Gonzalez messed up a couple of fielding drills, Papelbon said, “Do it over.” Gio did. All fun but with a point. On Sunday, Gio was one of the first in the Nats’ clubhouse, perhaps a sight never before seen in Viera in February.

“I kind of liked that,” Baker said of the Pap corrections. “Means I don’t have to say it.”

New Nats manager Dusty Baker, left, talks with pitchers Jonathan Papelbon, center, and Max Scherzer. Both players are key for their on-the-mound skill as well as their in-the-clubhouse personality. (John McDonnell/The Washington Post)

Just as in Boston and Philadelphia, where Papelbon holds the all-time save record for both born-in-the-19th-century franchises, teammates can choose to feed off his utter-extrovert energy, his borderline crazy competitiveness and his 349 saves.

Or they can focus on his arrogant attitude and the possibility they will wake up to discover, as Manny Ramirez once did, that Pap just ripped him in a national magazine for “selfishness.” Pap still has a grievance pending against the Nats for the four-game suspension they gave him for the Harper fight. Just business, no ill feeling, he says.

“That fight was forgotten fast by the players themselves. Once in a while, guys have fights. So what?” assistant general manager Bob Boone said. Why believe Boone? He’s a Stanford grad. He won seven Gold Gloves as a catcher. His father was an all-star. So was one of his sons. Another son hit a pennant-winning home run. The Boones are baseball.

As a karmic twist, Harper’s reputation for team-leader-level maturity has taken a jump since he said this month that he hoped “Pap saves 55 games this year and wins the Cy Young Award.” Last year, Papelbon showed what immaturity and bad-for-the-ballclub behavior actually looks like. Bryce has seemed like the adult.

If this chemistry experiment works, with friend-to-the-world manager Baker, Papelbon and bubbly center fielder Ben Revere joining wacky Max Scherzer, fans may see a team — often tight under pressure the past two years — that regains some of the baseball-as-fun approach of 2012, when Michael Morse was team DJ.

“After all the things he’s been through, you know Papelbon’s not going to change. You don’t get him to change,” Boone said of the reliever’s visibility here. “It’s good to have someone on a club who’s outspoken, who’s not afraid of anything. In a game with a lot of alpha males, that’s what you’re looking for.”

Of course, every team in every camp has theories to explain why their flaws are actually virtues waiting to be born. To me, building your team with Pabelpon as one of the structure’s weight-bearing beams is a high-risk, medium-reward proposition. It’s the if-all-else-fails fallback position.

And all else did fail when no glittery closer materialized in the offseason as Craig Kimbrel, Aroldis Chapman and even Darren O’Day ended up elsewhere.

If Papelbon has lost his game, if his big personality is more divisive than invigorating, if his relationship with Harper erupts, we will be picking up the sad charred shards of the Nats’ exploded season from Fairfax to Bowie.

Nats fans were at spring training expressing the whole range of Papelbon reactions, including, “Can I take the fifth?”

“I wish they’d kept [Drew] Storen to be the closer and gotten rid of Papelbon,” said Frank Cramer of York, Pa. His friend Jerry Scarphe, from Viera, sees the exact opposite side. “This group was so dispirited by the end of last year. To bring the team together, you need to make amends,” Scarphe said. “I think Dusty is just the guy to bring ’em together.”

In baseball, the role of coincidence is underappreciated. If the Lerners’ first contract offer to potential manager Bud Black had been the one that some in the franchise suggested, Black might not have gotten huffy and Baker would still be growing grapes in his vineyard in retirement. Would Black have been a manager suited to handling the Papelbon-Harper Act II? I respect Black, but I doubt it.

If anybody can, it’s Baker, who got MVP years from both Barry Bonds and Jeff Kent, who fought and hated each other through six successful years with Dusty.

The Nats have circled the wagons — around Pap. It’s not just Hollywood that has script doctors. If this Papelbon rewrite works, everyone will look like geniuses, even if most of the grand plan was just born out of necessity and accident.

If it doesn’t, we can look forward to Jonathan Papelbon Bobblehead Day. Be careful when you get the doll home. If you look at it wrong, its head blows off.

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