3) Jeurys Familia
Jeurys Familia wound up developing into one of the best closers in Mets history. Low bar, sure, but his seasons in 2015 and 2016 were among the best the franchise has ever had from that position. He tied the Mets club record with 43 saves in 2015, only to break that with 51 in 2016. He had some postseason struggles along the way, but his first stint in Queens was nothing short of great.
After the Mets traded him to the Athletics at the 2018 trade deadline it felt like Familia's tenure with the team was over. It felt like an optimal time to move on from the right-hander as he was set to make a decent amount of money in free agency.
Familia did earn a large chunk of change as he signed a three-year deal to come right back to Queens and was set to make $30 million total. The Mets brought him back but not to close. He'd set up for newly-minted closer Edwin Diaz.
Everyone knows how awful Diaz's 2019 was, but Familia was just as bad if not worse. The right-hander posted a 5.70 ERA in 66 appearances and was practically unusable in any close game. For a Mets team that just missed out on the playoffs that year, all they needed was more reliability from Diaz and Familia to get there.
Familia's next two seasons were better as he settled in nicely into a middle relief role, but that's not what the Mets brought him in to be. His second tenure in Flushing turned out to be a huge disappointment.