Three weeks ago, Chris Kreider was helping Boston College claim the NCAA championship.

On Saturday, the 20-year-old, skating in only his sixth professional hockey game, was the New York Rangers’ best player in a 3-1 victory over the Washington Capitals in Game 1 of the Eastern Conference semifinals.

Kreider notched the game-winner, earned the primary assist on the insurance tally 90 seconds later and was awarded the Broadway fedora, the hat given to the Rangers’ most valuable player after victories.

He also gives the Capitals one more Rangers forward to be concerned about.

“I’m kind of at a loss for words,” Kreider said. “I’m just trying to keep my head down and work hard.”

Skating on a line with Derek Stepan and team captain Ryan Callahan, keeping his head up helped the Boxford, Mass., native break open a tie game early in the third period.

As Capitals defenseman Mike Green headed toward the bench for a line change, Kreider saw an opening in the middle of the ice and used his considerable speed to race toward it. Stepan then threaded a perfectly placed pass through the neutral zone, hitting Kreider in full stride.

The Rangers rookie made the most of his chance. He wound up for a rare slap shot and caught Braden Holtby leaning, beating the Capitals goalie past the glove, to put New York ahead, 2-1, with 13 minutes left.

“I saw an opening, so I just tried to hit it,” Kreider said of Washington’s poorly executed line change. “I realized it was the end of my shift so I knew I needed to get it on net as fast as possible. . . . I don’t usually take slap shots. That was a little unorthodox for me. I just tried to put it on cage and it went in the goal.”

After the goal, the appreciative capacity crowd at Madison Square Garden began to chant his name.

“It was a surreal experience,” he said. “I got goose bumps. I was really tired after the goal but didn’t feel so tired when they started chanting.”

Less than two minutes later, Kreider set up Brad Richards, whose goal put the tightly contested game out of Washington’s reach. The play began with Kreider beating Capitals defenseman Karl Alzner in a puck battle along the wall and ended with Richards firing the puck through Holtby from point-blank range.

“Poise is obviously a big part of it,” Richards said of Kreider’s sudden success. “He’s not overwhelmed by anything. Hopefully he keeps it going. It’s been a nice surprise.”

For the Rangers and Kreider, who admittedly was unsure of what to expect when he left the Eagles earlier this year and signed a three-year entry level contract with the team that drafted him 19th overall three years ago.

A few days after signing, Kreider made his NHL debut in Game 3 of the Rangers’ first-round series against the Ottawa Senators as a replacement for Carl Hagelin, who had been suspended for three games. Kreider’s first NHL goal came in Game 6, and it also proved to be the winner.

He’s been wowing his new teammates ever since with his speed and offensive instincts.

“It’s pretty impressive,” defenseman Ryan McDonagh said. “We knew he could skate and move his legs. We just told him to keep moving his legs, chasing pucks down. That makes it really hard for the defending team to stop that because of his speed. He’s a quick learner.”

McDonagh also joked that Kreider asks a lot of questions, sometimes while on the ice.

“He’s asking more questions than he was in his first game,” McDonagh said “I’m sometimes worried. He’s asking me stuff right before the faceoff. I just tell him to keep his legs moving and listen to his forwards.”

Defenseman Dan Girardi added: “He proved once again why he deserves to be in the lineup. He fits right in with us and obviously is a good skater and offensively talented. We’re lucky to have him.”

When the Capitals learned they would be facing the Rangers, they knew all about the importance of shutting down Richards, Callahan, Hagelin and Marian Gaborik.

Now they can add Kreider to that list.

“He’s a good player, a first round pick,” Capitals Coach Dale Hunter said. “He can skate and he knows the game.”