Junior Burgos is congratulated by a teammate after his second-half performance. (Photo courtesy of the Cosmos)

NEW YORK — Boston City FC and the National Premier Soccer League were introduced to the lethal right foot of Junior Burgos on Saturday night.

Within a 15-minute span late in the New York Cosmos’ 5-0 triumph at Mitchel Athletic Complex in Uniondale, N.Y., the El Salvadoran international midfielder scored twice off free kicks, leaving the crowd of 5,121 cheering and coaches and teammates using superlatives to describe the goals.

“Two amazing goals,” head coach Carlos Mendes said.

“That’s fantastic to have a weapon [like that],” added Mendes, who had to defend against Burgos’ free kicks when he played with the Cosmos. “I’ve known from before, even playing against him how dangerous he is. Today, great, great goals, the way he finished them. The pace, the accuracy.”

“Oh man, that guy’s deadly on the set pieces,” said midfielder Joey Sanchez, who scored a goal. “It’s good to have that. Sometimes you need that. We’re lucky enough to have him.”

Luck, of course, has nothing to do with Burgos’ ability to turn a free kick into a goal. It takes talent, practice and experience.

He has lost track of how many times he has celebrated free-kick goals.

“I don’t have an exact number, but I definitely have made a couple in important games,” the veteran midfielder said. “Sometimes a free kick can be the difference between a win and tie. Today we were lucky enough to score five goals.”

Burgos, 30, had scored twice directly from set pieces only once before in his career, which made this accomplishment special.

“To be able to score my first goal as a Cosmos player in front of these fans who came out tonight was really special,” he added.

And special for another reason — the goals were an early Mother’s Day present for Burgos’ mother, Moreno. His sister Fatima attended the game.

“It was a just special moment for me,” he said. “I’ve been working a lot to get up to my level and today hopefully is the start of a good season.”

Burgos was forced to sit out the Cosmos’ opening two games due to a suspension by the El Salvadoran Football Federation. He made his Cosmos debut in Wednesday’s 2-1 first-round victory over Black Rock FC in the Lamar Hunt U.S. Open Cup last Wednesday night.

The key to a successful free kick?

Well, practice, practice, practice.

“I try to get my technique right,” Burgos said, adding that he and several teammates stayed after training Friday “to take a lot of free kicks and make sure that if we had an opportunity in the game we’d know that it was a tool that we could use. We had a couple today we should have scored more than two.”

More? Now, that’s a dangerous thought.

With the Cosmos enjoying a 2-0 lead in the 75th minute, the 5-11, 172-lb. midfielder attempted a free kick some 30 yards out on the right side that he powered past goalkeeper Jason Katz.

“The first one I was a little bit further out,” Burgos said. “I had to get a little bit of power behind the ball. The first free kick I took in the first half I tried to hit it around the wall, and it didn’t work. So, I knew I needed to hit it over the wall. Luckily, I put it in a place he [katz] couldn’t get to.”

The second free kick tied a bow on the Cosmos’ win in the 90th minute as Burgos took this attempt from 20 yards out on the left side, drilling it into the right corner. It turned out to be the final kick of the match.

“I felt he was going to cheat to the first post, so I switched it up to the second post,” he said. “It hit the top bar and it went in, so it was good.”

Burgos said his first goal was his favorite “because it was a lot further out. It was my first goal as New York Cosmos player, and it will be one that I remember for a long time.”

After a scoreless first half, the Cosmos stepped up their game, scoring five goals in the final 45 minutes.

“I felt like the first half we came out a little bit flat. We were not in rhythm,” Burgos said “We were not playing our style of game. I thought the second half, the substitutes that came on injected us with a lot of power and a lot of intensity. I felt like the adjustments worked out great. We picked up the intensity. The halftime speech was really important by Carlos. We came out and tried to win the game.”

Mendes liked what he saw from his team and Burgos.

“He stepped his game up in the second half in general,” he said. “Outside of the two goals I thought he was much more involved and building and creating for us. Yes, he’s a vital player. If he’s on the ball and he’s moving it quickly for us, he can hurt the other team. Outside of the two amazing goals, and something we were very aware of on set pieces, just a better second half and getting on the ball and making sure he started the attack more.”

The next challenge for Burgos and the Cosmos will be against Hartford Athletic in the Open Cup’s second round in Hartford, Conn. on Tuesday at 7:30 p.m.