The all-time single season performance Mariners rotation

The Seattle Mariners have had two Cy Young Award winners in their history, but there have been more than two great pitchers in franchise history. Building a rotation of the five greatest Mariners is straightforward, so I will be building a rotation of the five best single-season performances in franchise history. 

To avoid the rotation being filled with the same player multiple times, a player will only be represented once by their best season in the PNW.

Mariners 2014 Félix Hernández 

Choosing between the Cy Young 2010 and the ‘14 season was not a straightforward decision. In terms of WAR, his ‘10 season was move valuable (7.2 WAR to 6.4 WAR), and he actually won the Award for being the American League’s best pitcher, but a second-place finish in ‘14 is as close as you can get.

The reason that the non-Cy Young winning season is the choice is that King Félix’s stuff was better. He struck out batters at a higher rate, gave up fewer hits and even had a lower walk rate. 

In every rate stat, he was better, and with a lower ERA, winning more games and more, his ‘14 season comes in as the best of his career. 

Comparing the two years: 

2010: 13-12, 2.27 ERA, 249.2 innings, 1.057 WHIP, 7.0 H/9, 2.5 BB/9, 8.4 SO/9

2014: 15-6, 2.14 ERA, 236.0 innings, 0.915 WHIP, 6.5 H/9, 1.8 BB/9, 9.5 SO/9 

Mariners 2003 Jamie Moyer 

One of the greatest inning-eaters in MLB history, Moyer pitched a quarter-century. His best season came in his 40-year-old campaign in Seattle, being his one All-Star Game nod of his career. 

Being one of the most underrated pitchers of all time, Moyer is a perfect fit for the rotation and his ‘03 deserves its flowers. 

In that season, he went 21-7 with a 3.27 ERA. Never the most overpowering pitcher, he worked around striking out only 5.4 batters per nine innings to limit runs. His 132 ERA+ was the best of his career over a full season, and his fifth-place finish in Cy Young Award voting was the best of his career. 

Mariners 2013 Hisashi Iwakuma

Iwakuma only spent six years in MLB, but by far, his best season was his fantastic performance in ‘13. His 7.0 WAR was by far the best of his relatively short career, and the season was his lone All-Star Game nod and his third-place Cy Young Award finish was the one time he got votes for the Award.

The righty from Japan went 14-6 with a 2.66 ERA, pitching 216.2 innings and striking out 185 batters to 42 walks. His 138 ERA+ was the best of his career and one of four seasons, he was an above-average pitcher. 

While he does not have the longevity or prolonged success to make the Mariners’ Hall of Fame, his ‘13 season deserves a spot on this list. 

Mariners 2023 Luis Castillo 

This choice is working under the assumption that Castillo is going to continue his current production through the end of the season. Well, on his way to a top pitching performance in team history, Castillo has made 13 starts for the ‘23 Mariners and has been great so far. 

Currently pitching to the tune of a 2.70 ERA, Castillo is maintaining a 0.991 WHIP, 10.8 SO/9 to 2.0 BB/9, while limiting batters to just 6.9 H/9. 

Even if his production dips slightly, he is well on his way to one of the more impressive pitching seasons in the PNW, with this list serving as the official prediction that he will not only maintain his production, but potentially even slightly improve.