2) Devin Williams
The rotation is obviously an area of the roster the Mets must improve, but the bullpen is arguably in even worse shape. Edwin Diaz coming back is obviously huge, and Brooks Raley's club option being exercised means he'll be back, but who else is there? After Adam Ottavino rejected his player option it looks like he could be gone. That means guys like Drew Smith and Trevor Gott are probably the Mets third and fourth-best relievers right now. That's obviously a major issue.
The Mets will need to look to add multiple relievers to the roster, but not all of that work has to be done in free agency. New York could look to the trade market and if they were to make a deal with Milwaukee, Devin Williams is a player they'd at least have to inquire about.
Williams was a preimier set-up man for Josh Hader in Milwaukee and just put together a terrific year for the Brewers as the team's primary closer after they dealt Hader away at the 2022 trade deadline. He had 36 saves in 40 tries this past season while posting a 1.53 ERA in 61 appearances.
Williams would revert back to a set-up role with the Mets, and is a player they'd be guaranteed to roster for more than one year. He won't be a free agent until after the 2025 season. This would ensure the Mets have the best late-game duo in baseball with Williams and Diaz, at least for the short-term.
He wouldn't come cheap, but adding an arm like Williams could make sense if the Mets strike out in free agency.