Atlanta selected defender Donny Toia of the Montreal Impact with the first-overall pick in the five-round Major League Soccer expansion draft.
Toia, the Canyon del Oro High School product and former FC Tucson standout, was traded later in the day to Orlando City in exchange for the eighth-overall pick in next year's SuperDraft.
Minnesota United, the league's other new team, selected right back Chris Duvall of the New York Red Bulls with its first selection. Duvall, 25, had been with the Red Bulls since 2014.
Within hours, Minnesota traded Duvall to the Impact for winger Johan Venegas.
Atlanta also drafted veteran defender Zach Lloyd of FC Dallas, defender Mikey Ambrose from Orlando and Alec Kann of Sporting Kansas City.
Atlanta dealt Irwin back to Toronto in exchange for defender Mark Bloom and general allocation money.
"Our hope was to not lose anyone in the expansion draft. No matter how you work your protected list, due to the depth of our roster we knew it was a possibility and we had to prepare accordingly," Toronto FC general manager Tim Bezbatchenko said. "We are pleased to have Clint back and wish Mark and his family all the best in his home town of Atlanta and thank him for his four years of contributions to the club."
Atlanta was widely rumored to be interested in U.S. international goalkeeper Brad Guzan, currently with Middlesbrough in the Premier League.
Following Duvall, Minnesota took midfielder Collen Warner from the Houston Dynamo, midfielder Mohammed Saeid of the Columbus Crew, goalkeeper Jeff Attinella of Real Salt Lake and forward Femi Hollinger-Janzen of the New England Revolution.
For the expansion draft, each existing MLS team was able to protect 11 players, including designated players with no-trade clauses and homegrown players.
Atlanta appeared to have a significant jump on building its roster, with head coach Tata Martino signing some promising young players including Miguel Almiron of Paraguay, a 22-year-old attacking midfielder who has been with Lanus of Argentina's top division since 2015.
