Seattle Mariners’ Pitching Proves to be Elite in a Tough Season

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I spend a lot of time talking about what the Mariners aren’t good at. Their hitters are all collectively in a slump, and it makes every game feel impossible, particularly when they were held scoreless for several innings in each of the first two games against one of the historically worst teams of all time, the 2023 Oakland Athletics.

But they’re still always in the game for a very distinct reason: they pitch very well. Obscenely well, you could say. Marco Gonzales has a 4.74 earned run average, allowing 13 earned runs across 24.2 innings pitched. This gives him an ERA+ of 89, or roughly 11 percent worse than the average MLB pitcher. There are two interesting points of context here. The first is that this ERA is ridiculously inflated by one particularly bad start, where he gave up eight runs in three innings against the Toronto Blue Jays. The other is that he is by far the worst pitcher in the Seattle rotation:

  • Logan Gilbert boasts a slightly above-average ERA mark of 4.01 and is somehow the next-worst pitcher in the rotation, despite half of his starts still qualifying as “quality starts.” These are outings where the starting pitcher throws six or more innings while allowing three or fewer runs.
  • George Kirby, in his sophomore campaign after an impressive rookie season, boasts a 2.93 ERA (143 ERA+) through his first five starts and escaped the month of April with just two walks total. He has set the record for strikeout-to-walk ratio in his first 30 career starts, as well as the fewest walks through a pitcher’s first 150 career strikeouts with just 23. Kirby also posted the first complete game of the Mariner season, a 1-0 shutout loss against the Philadelphia Phillies.
  • Luis Castillo is everything the Mariners could have asked for. He’s allowed just seven runs in 34.2 innings in his first six starts. His 1.82 ERA is the third lowest in the American League. His 231 ERA+, which calculates to being 131 percent better than the average starter, is also third in the league. He is also the active leader in fielding percentage as a pitcher, which isn’t as important but is kind of neat.

What the Mariners, on paper, distinctly lack is a fifth starter in the rotation. Robbie Ray recently announced that he would have to undergo surgery and would miss the rest of the season. Chris Flexen has not been great in the rotation, but it looks like he won’t have to be. The Mariners got two critical starts from players making their Mariner debut this season.

The way Easton McGee got his first career start and second career appearance was astonishing. Against the very potent Blue Jays lineup, he took a perfect game through 6.2 innings before allowing a double to Matt Chapman. The Mariners would go on to lose that game, and McGee would immediately land on the 15-day injured list.

Enter Bryce Miller, the fourth-round pick by the Mariners in the 2021 MLB draft. Only the fourth player from that draft to make their MLB debut, he took to the mound in the season opener against the Oakland Athletics on May 2. He took a perfect game through five innings before allowing a run on two hits in the sixth. The Mariners would go on to win 2-1, although Miller didn’t get the win as he was out of the game before Seattle could score. Miller also set the record for most strikeouts in a Mariner’s MLB debut. Furthermore, there have been three pitchers to throw 10-plus strikeouts with no walks in their MLB debut: Stephen Strasburg in 2010 and Johnny Cueto in 2008 were the others.

The Mariner bats have been anemic, to say the least, but the elite level of pitching they are able to put forth day after day keeps them in every game and is a spectacle to watch. Hopefully, they can put together a solid homestand against the Houston Astros and Texas Rangers.