Herrera opted out of his minor-league contract with the Mets on Tuesday, Jon Heyman of MLB Network reports.
Herrera evidently wasn't satisfied with his current position in the Mets' farm system, so he'll head to the open market. He last appeared in the big leagues with the Reds a season ago, slashing .184/.268/.414 with five homers and 11 RBI over 53 games.