Even before he scored the winning run in Thursday’s dramatic comeback victory over the Chicago Cubs, Brandon Nimmo couldn’t stop smiling.

Nimmo, the 23-year-old rookie who was called up last week to replace the struggling Michael Conforto, may well have been the only person in the Mets universe doing so. Heading into Thursday’s game, the Mets had been swept by the rival Washington Nationals, ceding a six-game division lead, and the team’s lineup had begun appearing on local milk cartons.

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