Hart was designated for assignment by the Mets on Sunday, Tim Healey of Newsday reports.
Hart was likely hoping to be recalled for September's roster expansion, but he instead loses his spot on the 40-man roster in favor of infielder Sam Haggerty. Hart delivered 7.2 scoreless frames between the Brewers and Mets this season, but he had more lackluster results (4.43 ERA and 1.52 WHIP) at Triple-A Syracuse.