Atlanta United’s defense, often overshadowed by its offense, has been among the best in MLS this season.

It’s not just that it is tied for the league lead in shutouts (three) through seven games. It is that it is stifling opponents because of a combination of formation, tactics, chemistry and intensity. The team will host Montreal at 1 p.m. Saturday at Mercedes-Benz Stadium.

Among the stats tracked by Opta, which is used by the league,  is Big Chances, which is a situation where a player should reasonably be expected to score, typically in a one-on-one situation from close range. The Five Stripes have allowed just 11 Big Chances, tied for fifth-fewest or 1.57 per game, which is third-fewest. Throw out the four Big Chances that happened in the season-opening 4-0 loss at Houston, and Atlanta United has allowed just seven Big Chances opportunities in the past six games.

Stifling.

“Maybe the strength of the team has appeared to be the backline of the three or five, but I’d like to highlight the work that the whole team is doing,” Atlanta United manager Gerardo Martino said.

Martino hit on several factors to the team’s defense, which last season allowed the second-fewest goals (40) in the Eastern Conference.

The first, and most obvious, is the 3-5-2 formation. Martino used it a few times late last season, but has gone to it extensively during the team’s six-game unbeaten streak. The formation is defensive-minded because it includes three centerbacks, two wingbacks, a defensive midfielder and a bridge midfielder who tracks back on defense and gets forward on offense.

“It gives us a little more security in the back, especially when we are dropping deep,” captain and centerback Michael Parkhurst said.

As long as Parkhurst, Leandro Gonzalez Pirez and Chris McCann, the three centerbacks, and defensive midfielder Jeff Larentowicz stay compact, it is difficult for opponents to find good angles from which to shoot. That is a reason why Atlanta United’s expected goals-against for the season is 8.86, the fifth-lowest total in MLS this season.

“Our first thought is to stay compact and see if we can’t give up any chances in and around the box,” wingback Julian Gressel said. “It’s worked.”

Within the formation, Atlanta United’s players, particularly those on offense, understand when to press and when they do so are tenacious. That relieves the pressure on the backline.

“You’ve seen in the last two games against New York City and against L.A. that our intensity has been really high,” Martino said.

The pressing tactic is slightly different than last year when Parkhurst said it was a lot of man-on-man all over the field. That created opportunities for opponents to counter-attack. This year, not so much.

“Rarely are we one-on-one anywhere on the field, there’s always a little extra help,” Parkhurst said. “I think that is first and foremost the big change. The whole team has bought into doing their job defensively, being there to support teammates. Guys are working hard.”

An example came last week against the Galaxy. Los Angeles had broken through Atlanta United’s back line. The ball was sent to the back post, where there was an unmarked Galaxy player. Darlington Nagbe, the “bridge” midfielder, saw the danger and sprinted back to head away the dangerous ball.

“We are all working to get back now,” Nagbe said.

McCann said having a year of playing together has also helped. Not only do the players better understand each other, but the coaches and players better understand each other. He said Martino doesn’t waste any sessions during training. Every segment is designed to improve fundamentals or go over scenarios that the team will experience during a game.

“We know that if we limit the other team, limit their chances, even scoring one goal against, we are going to give ourselves really good odds to win the game,” Parkhurst said.