Flexen was released by the Mets on Thursday, Tim Healey of Newsday reports.
Flexen was designated for assignment by the Mets shortly after they acquired him from the Mariners on Monday as part of a three-player swap. The primary target for New York in that trade was reliever Trevor Gott. Flexen, who had struggled to a 7.71 ERA in 42 major-league innings this year with Seattle, will now head to the open market.