Rosario’s error comes at worst time for Syndergaard, Mets

Modal Trigger

The Mets' Ahmed Rosario, left, who made a costly error in the eighth inning Thursday, scores in the seventh.ST. LOUIS — This has been a difficult start for Jose Reyes, but one of his jobs is to keep young shortstop Amed Rosario in a positive frame of mind. He has Rosario’s back.

Rosario made his third error of the season in Thursday’s 13-inning, 4-3 Mets loss to the Cardinals at Busch Stadium. That error allowed the Cardinals to get leadoff hitter Greg Garcia on base in the eighth, and eventually Garcia scored to tie the game at 2-2.

With Noah Syndergaard pitching a gem and the Mets leading 2-1, Rosario was playing up the middle on Garcia, and the ball was hit more toward the…