Kelly Johnson--Since Mike Fontenot got a contract, Kelly Johnson is my new guy. He's got all the makings of a good bench-guy: left-handed and defensively versatile. As a secondbaseman, Johnson has the bat for the position, but a suspect glove, basically what you might expect from the Daniel Murphy 2B project that never was, and not my dream replacement for Castillo. Still, given his nice combination of discipline and power, "platooning" him with Castillo and using him to spell Francoeur versus the occasional righty would be effective. If the Mets sign KJ, I predict he takes Castillo's job no latter than June.
Matt Capps--Capps will never live up to the closer billing he inherited in Pittsburgh, but he has consistently posted xFIPs ~4.00 since making it to the majors. An inconsistent fastball lead to Capps getting tagged for a lot of homers last year, but I guarantee, with a more liberal budget, the Pirates held onto this guy. The Mets have some holes to fill in their pen, and they could do (and probably will do) a lot worse than Capps.
Jack Cust--I'm torn. If a team gets Jack Cust to accept a bench role, there won't be a better lefty pinch-hitter in the majors. That said, Cust will probably look for a DH job elsewhere, and the last-in-UZR Mets might want to look for another type of fourth "outfielder."
Ryan Garko--Mets fans are already clamoring for Ryan Garko as the perfect platoon-mate for Daniel Murphy. He has a .885 OPSvL and a reasonable 1.17 platoon ratio, so the ability to hit lefties is real. Garko, however, has no other attractive talents. He can't field, play anything but first, hit righties, or run. Keeping him on the bench just to relieve Murphy against lefties isn't a very productive use of a roster spot, especially since Manuel will end up pinch-hitting him against righties too often. If anyone wants to convince me Garko is more deserving of a roster spot than Nick Evans, who hits lefties nearly as well, with the added ability to play outfield and emergency catcher, good luck.
As an aside, I'm still perturbed at how easily Mets fans accept this Daniel Murphy-platoon garbage as a good plan at firstbase. What if the Bears are who we thought they were, and Daniel Murphy reprises his role as the worst offensive firstbaseman in the league? What if Ike Davis isn't the super-star of the future? As fans, we often don't realize just how possible these outcomes are. Here's a novel idea I threw out earlier: go get a real firstbaseman. Anyone? No? All I'm saying is, if the Phillies acquire Roy Halladay, I think the only reasonable--no, patriotic--thing to do is trade the farm for Adrian Gonzalez.
Garret Atkins--Although a incentive-laden deal would be tempting, I still have trouble finding where Atkins would fit on the bench. He's basically Ryan Garko with more upside, but also considerably larger and more likely downside.
Ryan Langerhans--The Mariners replaced Endy Chavez with Ryan Langerhans and the Mariners are smart, so let's do that too. Good BB% and decent power make for a league-average hitter with tremendous defensive ability.
Request any I skipped, and I might add them.