Diehl and Tyler Naquin were traded from the Reds to the Mets on Thursday in exchange for Jose Acuna and Hector Rodriguez, Robert Murray of FanSided.com reports.
Diehl began the season pitching out of the big-league bullpen for Cincinnati but was designated for assignment after allowing seven earned runs across his first 5.2 innings. He has pitched with Triple-A Louisville since, but he may have the opportunity to work low-leverage innings with the Mets.