(Reuters) - Gerardo "Tata" Martino has resigned as head coach of Lionel Messi's Inter Miami, according to multiple media reports, after the team suffered a surprise defeat to Atlanta United in Round One of the MLS Cup Playoffs.

Miami looked set to cruise to the championship after a record-breaking 74-point regular season but lost the best-of-three opening round in a shock upset to the ninth seeds Atlanta earlier this month.

Martino, who coached Messi for the Argentina national team and at Barcelona, joined Miami last year.

He is set to appear at a press conference on Friday with Managing Owner Jorge Mas. Media reports cited "personal reasons" as his reason for stepping down.