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

Luis Castillo - Four Seam Fastball

Usage: 44.4%
BA: .165
Whiff Rate: 33.0%
Strikeout Rate: 32.8%
Total Run Value: 19

While he was known for having an excellent changeup in Cincinnati, Castillo has been all about the heat since coming to Seattle. High fastballs have been all the rage since 2017 when analytics teams began to notice that they increased whiffs and decreased hard contact. Castillo's style has paired well with this new trend, with sliders and sinkers covering the rest of the zone. Great control and an average velocity of 96.3 mph are what allowed him to have one of the best fastballs in MLB.

George Kirby - Four Seam Fastball

Usage: 39.4%
BA: .234
Whiff Rate: 28.0%
Strikeout Rate: 28.4%
Total Run Value: 14

Kirby is one of the most exciting names in pitching. He led all of baseball in walk statistics last year with a 2.5% walk rate, 0.9 BB/9, and 9.05 K/W. One contributing factor to this performance was his willingness to attack the strike zone with extreme aggression, powered by his four-seam fastball. While not quite as effective as Luis Castillo's, Kirby put up similar strikeout numbers while also concentrating his pitches in the upper part of the zone.

Bryan Woo - Four Seam Fastball

Usage: 46.9%
BA: .207
Whiff Rate: 30.3%
Strikeout Rate: 31.3%
Total Run Value: 7

Despite filling in the last spot in the rotation, Woo's fastball did some serious damage in his 18 starts. He averaged 95.1 mph and thrived at the top of the zone, posting whiff and strikeout numbers very close to Luis Castillo. He was held back by a somewhat high slugging percentage of .407, but Woo's fastball could be considered among some of the best when things were rocking and rolling.