Matt Niskanen, above, forced Vegas goaltender Marc-Andre Fleury to leave the crease and commit a penalty late in the second period to wipe out a Golden Knights power play. (Geoff Burke/USA Today Sports)

Matt Niskanen’s long strides carried him down the ice as the puck sailed in front of the Washington Capitals defenseman with less than 30 seconds remaining in the second period of Game 3 of the Stanley Cup finals Saturday at Capital One Arena.

Working to kill off a penalty and with Vegas defenseman Shea Theodore in his sights, Niskanen powered past Theodore and across the offensive blue line. As Niskanen drove to the outside of Theodore while the Vegas defenseman shot a quick glance to center ice, Theodore tripped, giving Niskanen a clear path toward the Vegas goal. 

But with Vegas goalie Marc-Andre Fleury forced out to defend, he was called for tripping on Niskanen, ending the Vegas power play and any chance of a momentum shift heading into the third period. Niskanen’s hustle exemplified the Capitals’ effort plays on both ends of the ice that propelled them to a 3-1 victory and a 2-1 series lead. 

“He is our rock back there,” Capitals center Jay Beagle said of Niskanen. “He is always making unbelievable plays, and that is huge, yeah, when guys make big plays or big blocks. … I think we carried over a little bit from Game 6 [against Tampa Bay]. We talked about it against Tampa, about how we need to play like that at home. That was something that we could build on, and I feel like we did that today.”

Both teams emphasized quick starts in the days leading up to Game 3. And while the game was scoreless heading into the second period, it was the hustle plays that had forced Vegas into a slow start. Washington’s Devante Smith-Pelly said effort plays like pushing it out on a penalty kill, drawing penalties and chasing down a loose puck are the “little things” that will be important for the rest of the series.

“It is really simple,” Capitals center Lars Eller said. “It is just commitment from all five guys and, even though we didn’t execute perfectly every time today, the commitment was there and the effort was there always, so we got better.”

On Saturday, the Capitals had 26 blocked shots to Vegas’s nine. Thirteen players blocked a shot for the Capitals.

“I think there’s more to blocking shots than just going out there and trying to get hit,” goalie Braden Holtby said. “We’re doing a great job of creating the right layers, guys going out there strategically to know which lane I’m picking for sightlines and they’re taking away the other half and making big blocks and that’s a huge part of why we’re having success defensively because it’s all through our lineup.”

Even captain Alex Ovechkin, who blocked two shots, was a key leader defensively. Theodore praised the Capitals’ defense, saying it was tough to find lanes but that the Golden Knights were also to blame for a lack of productivity.

“Tonight just called for a little bit more of that,” Smith-Pelly said. “Game 1 was different then Game 2, and tonight was different as well. It just kind of called for everyone to block shots tonight, and we are willing to do that.”

Postgame reading
Immerse yourself in the Capitals’ postseason with The Post’s coverage of the Stanley Cup playoffs:

Brooks Orpik returns to Game 3 after brutal hit, inviting scrutiny of NHL’s concussion protocol

The Capitals won. Look at the madness outside Capital One Arena.

Evgeny Kuznetsov shakes off the pain, delivers haymaker of a goal for Capitals

The Golden Knights have lost two straight for first time in the playoffs

In the District, this Stanley Cup finals game is as big as it gets

For Washington Capitals fans, the moment they have all been waiting for

Washington’s answer to Vegas: Sting, Shaggy, Fall Out Boy and Pat Sajak