PITTSBURGH _ The Mets are winless without Asdrbual Cabrera.
Hours after trading Cabrera to the Phillies, the Mets lost, 5-4, to the Pirates when Tim Peterson allowed a walk-off single to David Freese.
The teams have split the first two games of this series.
The Mets' (43-58) bullpen actually pitched well Friday night, but they were asked for at least 14 outs after another short start by Jason Vargas.
Vargas, who had been sidelined with a right calf strain, allowed three runs in 41/3 innings in his return from the disabled list. He gave up a two-run homer to Freese in the second inning, and also walked three batters in a laborious effort. His night ended in the fifth after 84 pitches with a man on first and one out and the Mets ahead, 3-2.
The lefty has yet to record an out in the sixth inning this season and has allowed seven earned runs in his four innings pitched.
Seth Lugo, who has been the Mets' best reliever this season, allowed that inherited runner plus another to score to put the Mets in a 4-3 hole. Freese punched a two-run single up the middle, and has now driven in seven runs in this series.
The Mets tied the game in the sixth by capitalizing on a Pirates error when left fielder Adam Frazier's throw home went to the backstop, allowing Michael Conforto to score. They settled for just that one unearned run despite loading the bases with no outs.
Conforto gave the Mets a 3-0 lead in the first inning by hitting a three-run homer to left off Ivan Nova. He went down and golfed a low curveball.
Peterson allowed two singles to start the ninth and the Mets issued an intentional walk to load the bases with no outs. Freese then gave the crowd of 26,356 a walk-off win to celebrate by lacing an RBI single into the right-center gap.
