Atlanta United FC’s first regular-season game ended with a 2-1 loss to the New York Red Bulls that left the sellout crowd of 55,279 grumbling about the officiating and the failure of another Arthur Blank-owned team to hold a late lead.

But the excitement and optimism about the Major League Soccer expansion team survived one disappointing result at Bobby Dodd Stadium, where United will play until Mercedes-Benz Stadium is ready.

Forward Yamil Asad scored United’s only goal in the 25th minute off a beautiful cross from Tyrone Mears, and United held the lead for more than 50 minutes with an aggressive style that produced strong possession time.

United Coach Tata Martino capitalized on the technical skills of players from the Argentinian leagues while honing the aggression familiar to South American play to complement the finesse of the North American league.

“It’s not that different from other teams necessarily. They have a determined style and want to compete for the playoffs,” Martino said. “They want to be aggressive and control the ball. They won’t be the only team to play like that — there are other teams in the league to play a similar style — but that’s the kind of style we want.”

But United is a young team that has trained together only since Jan. 23, including four preseason games, and its lack of cohesiveness showed as it surrendered the tying goal off a corner kick in the 76th minute, then lost on what was ruled an own goal by defender Anton Walkes six minutes later.

“We don’t know if it will be days or months or how long it will take for the team to come together, but hopefully you’ll see it in our first few matches,” Martino said. “Once we had all the players together, we tried to establish a clear form of how we want to play, and we did that by talking a lot, having team meetings and trying to get on the same page.”

Before the game ended, Carlos Carmona received the first red card in United history as frustration mounted on and off the field with the 17 fouls called against Atlanta.

The red card proved to be the last straw, and United supporters started throwing things onto the field.

The intensity of the fans reflected the years of hard work to bring a team to Atlanta. Sam Veal, the founder of the supporter club Resurgence, said Atlanta is ready for a change of sports environment.

“People weren’t sitting down, and that says a lot,” Veal said. “It’s speaking to a different population of sporting fans in the city. I’m very confident, when it comes to the passion of the fans, it’s something Atlanta is ready for.”

MLS Commissioner Don Garber agreed. He said the number of fans at Bobby Dodd Stadium left him speechless, and United has set a record by selling more than 30,000 season tickets its first year.

“I’m not sure any of our clubs have the size of the supporters they have, especially before their first game,” Garber said.

He said Blank was certain Atlanta had a strong soccer fan base when they began to talk about expansion in the South in 2008, and the first match proved that league expansion in the Southeast was a smart move.

“We wanted to be in this city when we were thinking about expanding south of Washington, D.C., when the league was a third of the size it is now. He said it to me back then, and he said it to me just now, that this is a great sports town, and people here love the city. It’s changing, it’s diverse, and there are lots of young people,” Garber said. “I think it’s another jewel in the crown of the city. I’m proud Atlanta is in Major League Soccer and really proud we can show images from today around the world.”

Veal said the loss reflected the team’s youth and inexperience but not its future. “I’m not worried about the loss. I left the stadium feeling very hopeful.”