Mets 2015 season: What changed?

Photo Credit: Kathleen Malone-Van Dyke

Photo Credit: Kathleen Malone-Van Dyke

Photo Credit: Jim McIsaac

Photo Credit: Newsday / Thomas A. Ferrara

Photo Credit: Newsday / Thomas A. Ferrara

The Mets began the 2015 season on a 13-3 roll that included a franchise record-tying 11 straight wins from April 12 to April 23. Since then, the Mets are 7-12 and their lead in the NL East has shrunk from 4.5 games to 1.5 games as of May 15. What changed?