Jay Beagle looks to pass around Adam Larsson of the New Jersey Devils in Washington’s 5-3 win on Oct. 10. (Patrick Smith/Getty Images)

Before Jay Beagle returned to Washington to report for training camp, his family threw him an early birthday party on their farm here, replete with a potluck dinner and a bouncy castle for the kids. “I don’t even know how many Beagles were there,” he said.

With that party, the Capitals center accepted his age — even if that 30-year milestone was, at the time, still more than a month away — and came to training camp with the singular focus of winning the third-line center spot. He’s long called it his dream job, although it’s not as if he’s settling for a bottom-six role; he just has the self-awareness to know it’s a position that best suits his defensive game.

Beagle won the job with very little preseason playing time, the Capitals’ coaching staff that confident in him. He now anchors a trio that is developing into a legitimate shutdown line for Washington, most recently containing a Chicago Blackhawks top line that included stars Jonathan Toews and Marian Hossa.

“There [are] times when you sense that” frustration, Beagle said. “That’s when you know you’re doing your job, just trying to play their top guys hard. It’s always been a goal to play in this role for me. I’m definitely not going to take it for granted. I’m trying to give it everything I have to stay in that third-line center position, and by doing that, I’ve got to shut down their top lines.”

When Coach Barry Trotz spoke about his third line, he attached a particular quality to each member. There’s the “heaviness” of right wing Tom Wilson, the speed of left wing Jason Chimera and, for Beagle, determination.

Trotz is so happy with the play of the line, in fact, that when center Nicklas Backstrom returned to the lineup Saturday, meaning some players naturally had to be shuffled around to fit him in, the third line was completely unaffected.

“We’re not there to kind of ‘fancy’ anybody,” Chimera said. “We get it done by grinding it out keeping it simple and doing the little things right. Just get pucks deep and go to work. It’s a fun style of hockey to play. It’s a playoff style of hockey.”

Trotz has been known to tinker with lines, but once this checking line came together in the team’s last two exhibition games, he simply let it be. Chimera started communicating to Wilson things that former winger Joel Ward would do, like staying in a certain spot when a play is developing.

Trotz started the trio against the Blackhawks on Thursday night because he especially liked the matchup of Beagle against Toews. After the Capitals’ 4-1 win, players pointed to the energetic first shift of that line for helping the Capitals break out of a habit of sluggish starts.

“They killed their top line,” winger Marcus Johansson said of the third-liners after the game.

Wilson’s hit on Toews in the first period led to an attempt at retaliation by Viktor Tikhonov, who was called for interference on Wilson. The Capitals went on the power play, and 17 seconds later, Washington had a 1-0 lead thanks to a T.J. Oshie goal, an example of the effect the Capitals’ checking line can have.

“That’s definitely the result of a good, hard hockey play,” Wilson said. “I’m not really focusing on going after Toews. I just found myself in a good position to make a good body check. It happens, and then one of their guys who doesn’t really have a history of much tough stuff comes over and takes a stupid penalty. That’s great for us.”

Said Trotz: “We’re not looking to hurt anybody, but [Wilson is] a big body that has to bump into people. I think when he’s playing against top people, it’s okay. . . . If they’re in his way, he’s got full reign to run them over.”

When the Capitals play the Calgary Flames on Tuesday night in the first stop of a three-game western Canada road swing, it’ll be the first time Beagle’s family will see him in his new self-described dream job. He guessed there would be 20 Beagles at Scotiabank Saddledome to watch him during the morning skate.

His actual birthday was Friday, and he celebrated with a cannoli, though he’s not one to indulge too much during the season. He doesn’t expect his mother to bake him a cake while he’s home; celebrations are behind him, and a new defensive matchup awaits.

“I’ll go home, and it’ll be all business,” Beagle said.