1) NY Mets catcher James McCann - 4 years/$40.6 million dollars
James McCann was coming off of a couple of really solid seasons as a member of the White Sox and the Mets rewarded him with a lengthy contract. This contract sticks out as the worst because the Mets could have had J.T. Realmuto that offseason but elected to sign the cheaper catcher instead.
Realmuto has remained the best or at least one of the best catchers in baseball while McCann gave the Mets absolutely nothing offensively during his two years here.
His at-bats were very hard to watch and his defense wasn't good enough to justify keeping him on the roster.
The Mets just traded McCann and had to eat a majority of his contract just to get another team to take him off their hands. It's a contract Steve Cohen I'm sure regrets hanging out but fortunately was able to get out from the contract without harming the farm system.
Four years for $40.6 million dollars isn't insane in terms of money but combining how bad he was with the fact that the Mets missed out on J.T. Realmuto that makes this the worst contract the Mets have handed out in the last ten years.