WASHINGTON — When the Capitals opened training camp on Sept. 19, the most intriguing battle on the roster was for a spot on the third forward line. The top six and fourth line looked locked in, the defensive corps — boosted by offseason acquisitions Jakob Chychrun and Matt Roy — appeared well-rounded and stable, and the goaltending duo of Charlie Lindgren and Logan Thompson was already set in stone.

Hendrix Lapierre and Mike Sgarbossa both had looks as the center on the line, and Sonny Milano, Aliaksei Protas, Andrew Cristall, Ivan Miroshnichenko and Jakub Vrana were all competing to be the wingers. Sgarbossa was the first player of the group to be cut; he went on waivers and was assigned to Hershey, Washington’s American Hockey League affiliate, over the weekend. On Monday morning, the Capitals assigned Miroshnichenko to Hershey and sent Cristall back to his junior team in Canada, the Kelowna Rockets, all but marking the competition as complete.

And when Washington released its opening night roster Tuesday morning, all was settled. Milano, Protas and Lapierre made the cut, and Vrana — who entered camp on a professional tryout — signed a one-year, league-minimum contract worth $775,000, returning him to the team with which he won the Stanley Cup in 2018.

“[Vrana has] had a great attitude. He’s worked extremely hard, had a good training camp,” Washington coach Spencer Carbery said Monday. “Saw some of the things that he can potentially do individually, but also some areas that he can help us as a team. Proud of him and the way he competed. His attitude was phenomenal throughout training camp. Trying to get back to the player that he was in the National Hockey League, and could potentially be a really good fit.”

The Capitals, who have both center Nicklas Backstrom (hip) and winger T.J. Oshie (back) going on long-term injured reserve, waited until Tuesday to confirm their roster because of salary cap gymnastics.

Because Backstrom was on LTIR during the offseason, he has to be on LTIR in the initial roster submission, but there was no such requirement for Oshie. Only placing Backstrom and his $9.2 million cap hit on LTIR on Monday — while sending Lapierre to Hershey (just on paper, to maximize cap space), with Oshie on regular injured reserve and a 21-player roster not including Vrana or Lapierre — got the Capitals within $170,000 of the cap.

Once Oshie was added to LTIR, Washington received additional salary cap relief in the amount of his $5.75 million cap hit. At that point, Vrana was signed and Lapierre returned to the NHL roster.

Carbery said the conversations with Miroshnichenko and Cristall, informing them that they hadn’t made the NHL roster this time around, were difficult. Both had solid camps, particularly Cristall. But both are young and in the early stages of their development. They will get much more out of playing top minutes in the AHL and in juniors than they will in the NHL, where they would have minimal playing time.

“Cristall had probably the best camp of sort of those guys, I would say, but there’s a lot more that goes into it of him and his development and being in the lineup every night,” Carbery said. “If he’s playing seven, eight minutes, does that help him as a player?

“I think Miro, as we saw last year, he can play in the National Hockey League. There’s no question about that. It’s, again, a young player that we’re trying to make sure is a big part of our future and we’re putting him in the best position possible to have a long, successful career and reach his full potential.”

Vrana, at 28, is a perfect fit as a 13th forward. There are no concerns about hampering his development if he’s scratched, and his speed and scoring pop will be valuable when he’s in the lineup. He also has had plenty of fans — both inside the room and in the stands — rooting for him as he competed to earn a contract.

“Such a great kid. I think he’s someone that we were all kind of rooting for throughout camp,” said winger Tom Wilson. “It’s been a lot of fun to have him around the rink. He’s a guy that kind of makes it a joy coming to the rink every day, to see the smile on his face. He’s a heck of player. We’ve seen what he can do, and I think he’ll complement the group very well. He’s put in the work. I think he’s grown as a player [and] as a person, and I’m proud of him for where he’s at now.”

Added Vrana: “On top of everything, just being able to get a chance to be back in the league, and on top of everything it’s with this organization and with this team. It’s great. I’ve been here before and had a great time. It’s great to be back here.”

Washington Capitals roster

Forwards: Nicklas Backstrom (long-term injured reserve), Nic Dowd, Pierre-Luc Dubois, Brandon Duhaime, Hendrix Lapierre, Andrew Mangiapane, Connor McMichael, Sonny Milano, T.J. Oshie (long-term injured reserve), Alex Ovechkin, Aliaksei Protas, Taylor Raddysh, Dylan Strome, Jakub Vrana, Tom Wilson.

Defensemen: Alex Alexeyev, John Carlson, Jakob Chychrun, Martin Fehervary, Dylan McIlrath, Matt Roy, Rasmus Sandin, Trevor van Riemsdyk.

Goaltenders: Charlie Lindgren, Logan Thompson.