ARLINGTON, Va. -- Carl Hagelin is out indefinitely after undergoing hip surgery, leaving the Washington Capitals without three veteran forwards as the season begins.

The team said Hagelin had an arthroscopic procedure Monday that is intended to address his chronically injured left hip.

Hagelin, 34, has not played since taking an errant stick to his left eye in practice March 1. He took part in some informal summer workouts at the team's practice facility but was not on the ice for the start of training camp.

"I hope for a good recovery for Carl," coach Peter Laviolette said following practice Tuesday. "He's such a good guy and such an important part of the team. ... He was one of our top penalty killers and so we'll certainly miss him on the ice."

The Capitals will open the season Wednesday without Hagelin, center Nicklas Backstrom and right winger Tom Wilson. Backstrom is also out indefinitely after hip surgery of his own, and Wilson is expected to miss at least the first month or two working back from a torn ACL in his left knee.

Aliaksei Protas is expected to fill one of those holes on opening night against the Boston Bruins. The big 21-year-old forward earned a spot on the roster with a standout training camp and preseason.

"I worked pretty much whole summer to make my dream come true," said Protas, who's expected to start at left wing on the second line with Dylan Strome in the middle and Anthony Mantha on the right. "I am close to it. Now I just need to work even more to prove I deserve to be here."

Darcy Kuemper, signed to a $26.25 million, five-year contract to stabilize Washington's goaltending situation as the starter, figures to get the nod against Boston, which opens without injured winger Brad Marchand and defenseman Charlie McAvoy. Kuemper is coming off backstopping the Colorado Avalanche to the Stanley Cup but will be busy making his Capitals debut while his old teammates are watching their championship banner be raised to the rafters.

"I won't be thinking about that," Kuemper said. "Not till after the game, for sure."

Newly signed backup Charlie Lindgren could start Thursday at Toronto but Laviolette would not commit to his goalie for the Maple Leafs game. Former Capitals goalie Ilya Samsonov is set to start for the Leafs.