Mariners pitchers most responsible for endless road woes

In 2024, Seattle's pitching staff was the only thing keeping the team above water. Unfortunately, it wasn't enough as they ultimately fell just a few games short of a postseason berth. But heading into 2025, it was assumed the quality would get even better or at least remain the same.

To say that the Mariners' pitching has regressed would be an understatement. Last year, their team ERA of 3.49 was tied with the Braves for the best in MLB. This year, their team ERA of 4.03 places them 17th in MLB, a steep decline. By far the biggest driver behind this regression has been their starting pitching woes and how they've struggled while on the road. But who has been experiencing the most drastic differences between their numbers at home and on the road?

These Mariners pitchers need to get it together on the road

George Kirby

Home ERA: 3.16, Away ERA: 5.74

Kirby's season has been full of ups and downs. His season didn't begin until late May due to right shoulder inflammation and it took him some time to get into his groove. At home, he has been as dominant as expected, but when he's not at T-Mobile Park, he has had some brutal outings.

Of the seven starts this year where he has given up four or more earned runs, five of them have been on the road. These include a recent pummeling against the Rays where he gave up 10 hits and seven earned runs in just two innings of work.

Kirby's season-long issues deserve a deep dive of their own, but a cursory glance shows that his sinker is the likely culprit for the increase in hard contact he has given up this year. Opposing hitters are slugging .509 against the pitch that's ideally meant to induce soft contact.

Luis Castillo

Home ERA: 2.79, Away ERA: 5.40

If you've only watched Luis Castillo pitch in Seattle, you might be surprised that he's on pace to have the least effective season of his career. That's because like Kirby, his worst outings have been in other ballparks.

By game score, his five worst outings this year were all away. He also struggled to pitch effectively against the Rays in their recent series, conceding five earned runs in four innings.

Unlike Kirby, Castillo's intrinsic pitching metrics have taken a material hit, namely the velocity on his fastball, which has decreased steadily every year since joining the Mariners.

Interestingly, he also shifted his arsenal to be more dependent on his fastball and less dependent on his changeup after being traded to Seattle, which explains why regression on his heater has coincided with less consistent results.

Logan Gilbert

Home ERA: 2.15, Away ERA: 5.29

Gilbert may be the starter with what may be the biggest home/away spread in MLB today. While pitching at home, his numbers are in line with Tarik Skubal's, while his away numbers are closer to Chris Paddack's. He has only given up more than three runs in five starts, all of which have been on the road. His brutal outing against the Phillies on August 18th saw him taken out of the game after giving up six earned runs in just two innings, a Herculean effort that required 65 pitches.

Surprisingly, Gilbert's peripherals are still off the charts with whiff (33.6) and strikeout (33.9) rates comfortably in the top decile of qualified pitchers and an elite 2.82 xERA. However, those only count for so much when opposing hitters slugging .500 against his slider, a pitch that has gone from the most valuable weapon in his arsenal to a run value liability.

He did have a good start in Atlanta while dueling Chris Sale, but the broader season sample makes Logan Gilbert the perfect illustration as to what has been going wrong for the Mariners this season. With all of the brutal road trips over the past month, it seems that the team has left all of their mojo back in SoDo.