Atlanta United, which will host Montreal at 1 p.m. Saturday at Mercedes-Benz Stadium, is second in the Eastern Conference with 16 points but leads the league in points per game (2.29).
Almiron, an attacking midfielder, is a big reason why the team made the playoffs in its first season and is unbeaten in its past six games this season. The left-footer has four goals and four assists and 13 goals and 18 assists in 37 appearances in MLS.
Almiron, 24, was named the MLS Newcomer of the Year last year. Atlanta United acquired him from Lanus in Argentina.
The MLS transfer window closes on Monday. The summer transfer window for European clubs will open on June 9.