(Alex Brandon/AP)

BOSTON – When the initial World Cup of Hockey rosters were announced on Wednesday afternoon, two Washington Capitals were among the 16 players listed for Team USA. But one name was missing: Matt Niskanen.

“I was pretty surprised he wasn’t on there, actually,” goaltender Braden Holtby said.

“He’s an under-the-radar top defenseman in the National Hockey League,” Capitals Coach Barry Trotz said. “I think Matt is making a really good case for himself. I mean, he plays on the power play, he’s a terrific penalty killer and he manages big minutes against the very top people in the league.”

As injuries have ravaged the Capitals’ blue line this season, Niskanen has become the team’s top defenseman. With John Carlson out for a second time this season with a lingering lower-body injury, Niskanen has been logging the most minutes and taking on point man responsibilities on the top power play unit. He’s scored four goals and added 23 assists, with more than half of his assists coming on the power play. With 27 points, he’s on track to eclipse his 31 points last season.

Niskanen is averaging the most minutes of his career, an average ice time of 24 minutes 31 seconds. He and defense partner Karl Alzner have blocked the most shots on the team, both also contributing on the penalty kill.

“It’s tough because players like that go under the radar,” Holtby said. “The things he does win hockey games. It might not show up on the stat sheet every night, but there’s a reason for where we are in the standings, and those guys, him and Alzy, those type of players don’t come by very often. We respect what they do in here immensely, and I hope he gets a chance because he deserves it.”

The World Cup of Hockey will be in Toronto in September, and the rest of the team rosters will be announced on June 1. Niskanen is considered to be on the bubble for one of the three remaining defense spots. Kevin Shattenkirk (St. Louis), Justin Faulk (Carolina) and Keith Yandle (New York Rangers) will also be vying for one of those.

Seven Capitals were selected to the initial World Cup rosters. Holtby will be one of three goaltenders for Team Canada. Alex Ovechkin, Evgeny Kuznetsov and Dmitry Orlov were named to Team Russia. Carlson and T.J. Oshie are on Team USA. Nicklas Backstrom is on Team Sweden.

The Capitals didn’t have a morning skate on Saturday, but don’t expect any forward line changes for Washington against the Boston Bruins. Nate Schmidt is expected to be back in the lineup, likely for either Taylor Chorney or Mike Weber. Trotz said goaltender Philipp Grubauer will start in Boston.