A look at the most dominant pitch used by every Mariners reliever

Andres Munoz - Slider

Usage: 48.6%
BA: .230
Whiff Rate: 48.3%
Strikeout Rate: 39.6%
Total Run Value: 3

Intrinsically, Munoz has a filthy slider. Averaging 88.4 mph with 30 inches of drop, it shouldn't be any surprise that opposing hitters whiff almost half the time and strike out almost 40% of the time. It was truly devastating in 2022, when he accumulated a whopping 20 run value over just 65 innings and had a .126 BA.

This year's slider had a batting average almost twice as high, driven by more frequent hard contact. Opposing teams may have spent more time scouting and he may have been affected by being promoted to the team's closer, but with a full offseason of preparation, this pitch should return to its former effectiveness.

Matt Brash - Slider

Usage: 50.5%
BA: .162
Whiff Rate: 48.5%
Strikeout Rate: 44.1%
Total Run Value: 15

Brash went from a somewhat shaky reliever in 2022 to a dominant force in 2023. Reducing his ERA from 4.44 to 3.06 was no easy task but with a new and improved slider, he became an anchor in the bullpen. This pitch averaged 88.8 mph, 31.4 inches of drop, and 11.8 inches of horizontal break.

While his slider is dominant, developing another plus-pitch (perhaps refining his slider?) would take him to a whole-nother level.

Gregory Santos - Slider

Usage: 52.6%
BA: .196
Whiff Rate: 37.5%
Strikeout Rate: 30.8%
Total Run Value: 17

The newest member of the pitching staff arrived from the White Sox in exchange for Prelander Berroa and Zach DeLoach. He was great in his first full major league season in 2023, posting a 3.39 ERA and is looking to be a promising arm. His style follows the theme, largely depending on a devastating slider that averaged 91.4 mph, 31 inches of drop, and 5.7 inches of horizontal break.

He'll be arbitration eligible in 2026 and a free agent in 2029, so assuming he's effective he might be a bullpen staple for the next several years.