ATLANTA — More than 70,000 fans packed into Mercedes-Benz Stadium on Sunday night to watch their hometown Atlanta United in the first leg of the Eastern Conference championship.

The collected masses wouldn’t have been wrong to expect a frenetic, up-tempo game featuring a high press designed to unsettle and create turnovers that lead to goal-scoring chances. Pressure, after all, is what the New York Red Bulls do. The style is the team’s trademark, the thing that earned it the Supporters’ Shield and the top seed in the playoffs.

But when the match started, the Red Bulls sat back and let Atlanta dictate the play. It was surprising … to everyone except the home side.

Atlanta, it turns out, expected New York to abandon its trademark pressure.

“We thought it was possible, given how they played against us the last time they were here and how they played against Columbus away last round,” team captain Michael Parkhurst said after an emphatic 3-0 victory.

“When we watched a bit of the film from the first time we played them here, they did something similar to what they did tonight,” Jeff Larentowicz said. “A couple of us looked at each other and said, ‘Maybe they do that.’ Once that transpired in the first half, we knew we could play a bit and open them up.”

It was the center back’s 32nd-minute cross that found Josef Martinez for the game’s first goal. Larentowicz had time and space on the right side of the field, taking a couple of touches before hitting a curling cross that drifted over center back Tim Parker and onto his teammate’s chest. Martinez easily beat Luis Robles for his 34th goal of the season, an MLS record.

“They were allowing me to come forward, maybe as part of their game plan,” Larentowicz said of the goal. “I picked my head up and Josef was in the box. I tried to pick him out. He takes it really well. He tends to do that.”

Despite being down 1-0, the Red Bulls stuck to their game plan. Chris Armas’ team was content to let the opposition have the majority of the ball while trying to limit its chances. In the first half, Atlanta won the possession battle 62 percent to 38, but completed just 71.5 percent of its passes, down more than 10 percent from the season average of 82.7 percent. At halftime, the Red Bulls hadn’t started a single possession inside the attacking third, despite averaging 6.4 in the first half this season, but Martinez and Miguel Almiron, first and second in MLS in shots on target, had just two combined.

The Red Bulls were a different team. The problem for the visitors was that United were, too. They were there to win, not to play pretty soccer.

“We don’t have to connect 30 passes to go to goal,” Parkhurst said. “We’re going to take what the game gives us.”

Atlanta attacked up the wings with man of the match Franco Escobar running rampant on the right side due in part to the absence of 2018 Best XI left back Kemar Lawrence. Still, the Red Bulls held on into the second half, even scoring a goal that referee Kevin Stott waved off after going to video review.

In the 71st minute, the team used to applying the pressure finally succumbed to the opposition’s. Almiron picked up a turnover in the midfield, then released a cheeky through ball that turned Red Bulls right back Michael Murillo and ended up at the foot of Julian Gressel. The former Providence College Friar’s low blast skidded across the face of goal, where it was met by Escobar’s left foot — “his goal-scoring foot,” according to Parkhurst — doubling the lead.

New York searched for something, anything, to take back home. It failed, and then some. In the fifth minute of stoppage time — 90 seconds after the Red Bulls forced Brad Guzan to make his first save of the game — Atlanta substitute Hector Villalba blasted a shot from just outside the penalty box that beat Robles for the trifecta.

The Eastern Conference championship isn’t over, but Daylight saving time is, and it’s getting dark early for the Red Bulls.

“I’m sure it will be different at Red Bull Arena,” Parkhurst said. “We expect to go there and face the type of team that pressed us the last time we were up there. We will be ready for the press and expect it.”

The 20,000 fans in Harrison, New Jersey, on Thursday also will expect a press. And they’ll get it.

Atlanta will, once again, be ready to do what it needs to do.

“It’s not pretty,” midfielder Greg Garza said. “Playoffs aren’t the prettiest games. What matters most is who comes out on top.”