Here are a few names that I think the team should consider, though three of the five are extremely unlikely:
Guillermo Barros Schelotto: Atlanta United is reportedly already in talks with the Argentine, who is currently managing Boca Juniors. Eales declined to comment, which is the team's policy regarding speculative personnel moves. Schelotto isn't an experienced manager, having only recently ended a playing career that included a successful stint in MLS in Columbus, where he helped the team win the MLS Cup in 2008.
Marcelo Bielsa: Currently managing Leeds in the England's second division, this is the man who was arguably the biggest influence on Martino from when he coached at Newell's Old Boys. Bielsa believes in attacking and typically uses a 3-3-3-1 formation that is similar to the 4-2-3-1 and 5-3-2 that Martino has used at Atlanta United.
Jorge Sampaoli: The Argentine most recently managed Argentina's national team in the World Cup in Russia. The results were … interesting. Like Martino, he also played for Newell's Old Boys. Sampaoli has been a successful manager at numerous clubs with a winning percentage close to 50 percent, which is fantastic in soccer. He reportedly has a fiery temperament.
Juan Carlos Osorio: This one is also unlikely, but may have happened had the timing been a bit different because Osorio recently resigned as Mexico's manager, and was later named manager of Paraguay. Maybe the native of Colombia hasn't signed the contract yet. He is familiar with MLS from managing Chicago and then New York Red Bulls. He coaches a flowing style of soccer that would work well with Atlanta United. Again, this is extremely unlikely to the point of being impossible.
Miguel Herrera: The Mexican is currently managing Club America, so it's extremely unlikely that he will be available or even interested. But he's had success managing several clubs, including Monterrey and Tijuana, as well as the Mexican national team. He managed Mexico in the Georgia Dome for one game. He's also a fiery personality.
Arsene Wenger: Wenger was famously the manager of Arsenal for about a million years before retiring/pushed out after the 2017-18 Premier League season. He believes in coaching an attacking style of soccer and would bring a resume to the club that could be argued would surpass Martino's with three Premier League titles, seven FA Cups and seven Community Shields. He has no problem using younger players. The knock on Wenger is that he hasn't won much of importance recently. He has reportedly said that he will begin managing again in January.