Atlanta has drawn level with an MLS record of 69 points (21-6-6) and can lock up the Supporters' Shield for best regular-season mark with a victory Sunday at Toronto. That would also ensure home-field advantage throughout the play-offs and a chance to host the MLS Cup title game on Dec. 8.
"This was not an easy decision to make," Martino said in a statement released by the team. "I have enjoyed my time with Atlanta United very much and am proud of what we have accomplished together in such a short time."
The former FC Barcelona manager and Argentina national coach said he would have no comment on his future plans until after the season.
ESPN reported that he has a verbal agreement to take over as head of Mexico's national team in December, looking to build on the success of El Tri reaching the Round of 16 at this year's World Cup in Russia. The Argentina native also was mentioned as a possible candidate for national team vacancies in his home country and the United States.
Meanwhile, Atlanta United is beginning a global search for its next coach, with speculation that that they will focus on a replacement from South American to keep alive the pipeline that Martino has established to the football-mad continent. Venezuelan Josef Martinez set an MLS scoring record this season with 30 goals, while Miguel Almiron (Paraguay) and Tito Villalba (Argentina) also emerged as two of the league's top players.
"From the beginning, his vision for Atlanta United was aligned with ours, and his level of experience, talent and leadership has been extremely valuable during this critical time," team president Darren Eales said. "He will be missed, but we understand and appreciate his reasons for moving on to spend time with family and take on new challenges."
Under Martino's leadership, United made the playoffs in its inaugural season and followed up with one of the best seasons in MLS history. This past weekend, Atlanta locked up a spot in the 2019 CONCACAF Champions League with a 2-1 victory over Chicago, ensuring the top cumulative record of any MLS team over the past two seasons.
But a new coach will be leading the team when it takes the field in February seeking a continental title.
"We are very grateful to Tata for his commitment to Atlanta United and for all he has done to help build our club during our first two years in the league," Eales said. "True to his reputation, he has been an incredible leader and has set us up for great success moving forward."
But Martino isn't leaving yet.
Heading into the season finale, United holds a one-point lead over New York Red Bulls in the race for the Supporters' Shield.
"Tata will leave our fans with wonderful memories of our first years, and will always hold a special place in the Atlanta United history books," Eales said. "We look forward to finishing this season strong together, and wish him nothing but the best in the future."
Martino made it clear that he was leaving Atlanta on good terms.
"The decision was not made for financial reasons," he said. "Negotiations with the front office were transparent and fair. It was simply the right move for me and my family at this time. The opportunity to build a team from the start does not come along often, and I am grateful to the club and to the fans for putting their trust in me to establish a solid foundation here in Atlanta. What is most important now is that the focus remain on our goals for this season."