New York City FC is officially moving on to the second round of the Audi 2021 MLS Cup Playoffs after defeating Atlanta United by a score of 2-0 on Sunday in the Bronx.

This year's MLS Golden Boot winner Valentin "Taty" Castellanos opened the scoring in the 49th minute for NYCFC, while defender Alexander Callens added a second just four minutes later to help secure the crucial victory.

"In the first [half] we needed to switch the play more, get higher, overload, and get players inside of the box. That is exactly what we did in the second half," said NYCFC head coach Ronny Deila after the game.

"The whole performance was a high-level game. Atlanta has so much quality on their team and play very good football. Atlanta is always a very difficult side to play against. Big, big credit to the team today."

Castellanos once again benefitted from his teammates' strong collective effort as he gave the Boys in Blue the lead in the 49th minute.

"[Taty] is dangerous inside the box and has confidence. We have a team that plays up in good situations. I always say that nobody shines alone, and when the team is good everybody shines," said Deila. "Of course, Taty has special qualities and gets himself into situations that allow him to do big things."

While Castellanos and Callens helped lift their team past Atlanta United with a goal apiece, it was the NYCFC defense which once again came up with a huge performance to keep their opponents off the board and seal the victory.

"We win these games because we are so good defensively as a team," said Deila. "We have conceded the least goals in the history of the Club this year and that is not a coincidence at all. We have players and a team that are working in both ways."

The opening goal – assisted by team captain Maxi Moralez on a sailing cross into the box – may not have rocketed off of Castellanos' boot with great pace, but it found the back of the net regardless.

"I was in the box and I had to take a shot on goal. Whether I hit it good or bad, the important thing is that it was a goal," said Castellanos after the game. "The good thing is it helped the team and I’m happy with the scoring streak I’m going through right now."

Moralez also helped initiate NYCFC's second goal with a well-struck shot to the top-right corner in the 53rd minute that was deflected off the crossbar by Atlanta's veteran goalkeeper Brad Guzan, but the ensuing rebound set up perfectly for Callens to head the ball in for his second goal of the year.

"I dedicate this goal to my family, to the entire team that always looks out for me, to all the people of New York that never lost faith, they were always cheering us on. Today, the atmosphere was spectacular," Callens said after the victory. "I think this victory gives us confidence to believe and know we can achieve a lot of things by doing what we did today."

The next test ahead for NYCFC on November 30 will be a tough one as they prepare to face this year's Supporters' Shield winners in the New England Revolution, who finished with the best record in MLS during the regular season at 22-5-7 (73 pts).

"If we can replicate what we did today, we have a good chance to win in New England as well," Deila said of the upcoming showdown.

Check out the top highlights from NYCFC's win over Atlanta United in the video below, and visit the link here for more information on the remaining MLS Cup Playoff fixtures.