4) Dellin Betances
For the better part of his eight-year career with the New York Yankees, Mets fans watch Dellin Betances pitch like one of the best relievers in all of baseball. He was a four-time all-star with the Yankees while posting a 2.36 ERA with them.
Injuries limited the right-hander to just one appearance in 2021, but the Mets still signed him to a one-year deal worth $10.5 million. He was expected to be a key contributor in a revamped bullpen which needed a late-game arm.
The right-hander wound up making 15 appearances for the Mets in the shortened 2020 season, but struggled mightily. He had a 7.71 ERA and had more walks (12) than innings pitched (11.2) and strikeouts (11). Additionally, Betances displayed diminished velocity on the mound. He averaged just 93.6 mph with his fastball in 2020 after consistently hitting the mid/upper 90's as a Yankee.
He made just one appearance in 2021 after accepting his player option before going onto the IL with shoulder issues. He would not make another appearance in the majors. To sum up, this guy who was expected to be a dominant late-game bullpen arm for this team that desperately needed it wound up posting a 7.82 ERA in 16 appearances across two seasons. Not great.