Diekman (1-0) picked up the win Monday against Atlanta, allowing one run on zero hits and one walk in an inning of relief. He struck out one.
Diekman appears locked into a spot in the Mets' Opening Day bullpen, Will Sammon of The Athletic reports.
Diekman signed a one-year, $4 million contract with the Mets on Friday, Anthony DiComo of MLB.com reports.
Diekman was activated from the paternity list by the Rays on Thursday, Marc Topkin of the Tampa Bay Times reports.
Diekman was placed on the paternity list Monday.
Diekman finalized a one-year contract with the Rays on Wednesday.
Diekman and the Rays are finalizing a major-league contract Tuesday, Jeff Passan of ESPN.com reports.
Diekman was released by the White Sox on Saturday, Daryl Van Schouwen of the Chicago Sun-Times reports.
Diekman was designated for assignment by the White Sox on Tuesday.
Diekman threw a scoreless seventh inning with two strikeouts to earn a hold Wednesday against the Royals.