#3: Hisashi Iwakuma: 2013 w/7.0 WAR
This was an incredible season, and there’s a strong argument that it’s the biggest surprise season we have EVER seen from a Mariners pitcher.
Back in 2012, Hisashi Iwakuma signed with the Mariners, and spent the season split between the bullpen and the starting rotation. He made 30 appearances, 16 of which were as a starter. He seemed pretty good, with a low 3s ERA, some walk issues, but an overall impressive showing for a Rookie who came from overseas.
Maybe we should have seen it coming. After he got into the rotation in 2012, he had a 2.65 ERA as a starter, and a 2.07 in his final ten starts. That 2.65 number would end up being very telling.
In 2013, Iwakuma would finish with a 2.66 ERA and a 3.44 FIP, with a 138 ERA+. He also brought the walks way down, from 3.1 in 2012 to 1.7 in 2013. That was a big reason his WHIP dropped all the way to 1.006, one of the best qualifying marks in all of baseball. He’d also finish 3rd in Cy Young voting because Scherzer had 21 wins that year, but a worse season overall.
Every other season, Iwakuma was a strong pitcher with a WAR in the mid-2s. 2013 was special though and easily takes 3rd in the best seasons by a Mariners pitcher.