Puello, 24, had cleared waivers, was removed from the 40-man roster and assigned to Triple-A Las Vegas on the eve of the regular season. However, he complained of back discomfort and the Mets were forced to rescind the move. Instead, Puello spent the last four-plus months on the disabled list collecting major league pay and service time.
He resurfaced in the Gulf Coast League on July 27 for one rehab appearance before complaining of more back discomfort.
Puello served a 50-game suspension in 2013 related to the Biogenesis scandal.
He hit .252 with seven homers and 37 RBIs in 318 at-bats in 2014 with Las Vegas after returning from the suspension.