Sosa, 21, is not signing as a Designated Player, and the team didn’t say if he was signed under MLS’ yet-to-be-finalized Under-22 Initiative. He was acquired from River Plate, where he made 21 appearances, on a multi-year contract. He has 13 appearances with Argentina’s U20 national team.
“Santiago is a holding midfielder who understands and reads the game exceptionally well for someone his age,” Atlanta United Vice President and Technical Director Carlos Bocanegra said in a statement from the club. “He broke through into the first team at River last year, experiencing numerous big matches in both Copa Libertadores and the Copa Diego Maradona, in addition to his time with Argentina U-20s.”