2. Mark Leiter Jr.
It's weird to think that Mark Leiter Jr. was starting games for the Cubs in 2022, and he was even designated for assignment last offseason. Thankfully the team brought him back on a minor league contract two weeks later; a contract that has paid dividends. As I mentioned, Leiter is one of the big three relievers who have held this Cubs bullpen together all year and he deserves major credit.
Leiter's heavy usage of the sinker and split-finger gets him a lot of ground balls (47.1%), which is a fantastic combination with Dansby Swanson and Nico Hoerner up the middle. Although he has struggled recently (honestly the whole team has though), Leiter is prime a candidate to take Alzolay's role.
The 32-year-old has tossed 63.1 innings this year with 77 strikeouts and a 3.41 ERA. To successfully close the game though, Leiter will have to keep his walks down as he's averaged almost a walk per inning pitched in his last 30 outings.