4) Matt Moore
The Mets needed to add another reliever in the bullpen last offseason. It felt rather obvious at the time, and was proven to be the case over and over again as the season progressed.
One reliever the Mets could've had for fairly cheap and very late into the offseason was Matt Moore, who signed a one-year deal worth $7.55 million to join the Angels in the middle of February. The former starting pitcher was coming off an unbelievable year with the Rangers out of their bullpen, and would've fit in nicely as a second lefty in the Mets bullpen.
Instead, GM Billy Eppler prefered to have relievers with options, and passed on a quality arm like Moore in favor of arms who are no longer in the organization. Moore went on to have another great year, posting a 2.56 ERA in 50 appearances for the Angels, Guardians, and Marlins.
The southpaw would not only give Carlos Mendoza another reliable lefty to work with, but Moore gives the Mets the option of being used to record more than three outs. He recorded four outs or more eight times last season, including a pair of appearances in which he completed two innings.
The Mets badly need bullpen arms, and Moore should be toward the top of their list.