Puello was in the visitors' clubhouse with teammates before the Mets' exhibition game Friday against the Texas Rangers at Globe Life Park, but did not take the field with the rest of the club for batting practice.
Puello was not slated to make the Mets' Opening Day roster and was out of options, so the club needed to pass him through waivers before sending him to Las Vegas. Other teams had the chance to claim Puello, but would have needed to keep him at the major league level.
Puello, who turned 24 on Wednesday, hit .252 with seven homers and 37 RBIs in 318 at-bats and had 13 steals for Las Vegas in 2014.
He was suspended 50 games on Aug. 5, 2013 for a Biogenesis-related infraction of MLB's joint drug agreement.