The Pirates released Walker on Saturday.
Acquired from the Mets on July 30 in exchange for minor-league lefty Nicolas Carreno, Walker's stay in the Pittsburgh organization lasted less than two weeks. He gave up two earned runs over one inning during his lone appearance out of the bullpen at Triple-A Indianapolis before Pittsburgh booted him off the 40-man roster Friday. Now a free agent, Walker will look to catch on elsewhere on a minor-league deal before the season comes to a close.