The Best Individual Pitching Performances from Each Starter in 2023

It's no secret that the Mariners have some of the best starting pitchers in baseball today. However, when evaluating pitchers over 20-30 starts, it can be easy to lose track of what they're capable of when they're at their very best. Using a metric called Game Score, let's see how just good our guys really are.

Here is MLB's definition for the stat:

Game Score measures a pitcher's performance in any given game started. Introduced by Bill James in the 1980s and updated by fellow sabermetrician Tom Tango in 2014, Game Score is presented as a figure between 0-100 -- except for extreme outliers -- and usually falls between 40-70.

A Game Score of 50 is considered "average," while a Game Score of 40 is deemed to be "replacement level." Game Scores in the 80s and 90s are widely regarded as impressive, and scores of at least 100 are exceptionally rare. Using Tango's formula, which is the version displayed on MLB.com, only nine of the 4,858 games started in 2015 resulted in Game Scores of 100-plus.

Luis Castillo - April 16th vs. COL (7.0 IP, 2 H, 0 ER, 0 BB, 9 K)

Game Score: 82

In a dazzling show against the Rockies in mid-April, Castillo was nearly unhittable, giving up just two singles on the way to striking out nine batters and giving up no free trips to first base. While the Rockies didn't field the most threatening offense in the league in 2023, they still had a league-average OPS against right-handed pitchers. In addition to his nine strikeouts, Castillo earned 19 swings and misses and topped out at 97.9 mph on his four-seam fastball, a stark difference from his changeup which sat around the 87 mph mark.

While known for his changeup in his days with the Cincinnati Reds, Castillo has definitely evolved his game to rely more heavily on his four-seam and sinker combination. In fact, his changeup was his least used pitch in 2023 and the worst pitch by run value (-9). He's decreased his total usage of the off-speed pitch over the past few years but with a similar movement profile and arm-side run, his sinker is just as good and will only get better. Meanwhile, his four-seam fastball had an opposing BA of just .165, so it's safe to say he won't be "changing that up" anytime soon.

Interestingly enough, the Mariners won this game 1-0 with the team barely enough run support to escape with the win, seemingly a team tradition for the team's great pitchers.

George Kirby - August 12th vs. BAL (9.0 IP, 3 H, 0 ER, 0 BB, 7 K)

Game Score: 88

In September, George Kirby drew the ire of many extremely qualified and unbiased baseball experts on Twitter when he stated in a postgame interview that he should've been taken out of a game against the Rays sooner. People conveniently forgot that less than a month earlier, Kirby had thrown 103 pitches against the Orioles over nine innings while giving up no walks and earning seven strikeouts. Against a team that went on to win 101 games, Kirby earned 15 whiffs and topped at 99.7 mph on his four-seam fastball. He also had spin rates of 2500+ RPM on his curveball and slider. To cap it all off, he earned his own 27th putout with a caught flyball off of Cedric Mullins.

It was only fitting that on a night meant to celebrate the immense legacy of Felix Hernandez, the Mariners would fail to add any run support and lose in the tenth inning, with Kirby unable to record a complete game shutout. Nonetheless, it was as if the King himself was back on the mound.

Bryce Miller - May 2nd vs. OAK (6.0 IP, 2 H, 1 ER, 0 BB, 10 K)

Game Score: 74

Bryce Miller burst onto the scene with an electric debut. After starting the year with the Arkansas Travelers in Double A and posting a lackluster 6.86 ERA across 19 ⅔ innings, he made the jump to the big leagues and immediately made his presence known.

In a classic Miller matchup, Bryce Miller and Mason Miller went toe to toe, trading blows until the Mariners finally came out on top 2-1. Bryce struck out 10 Athletics and earned 13 swings and misses over six innings. His four-seam fastball started at 97 mph before slowing down to 94 mph as he went deeper into the game while his slider/sweeper combo were a nice change of pace.

Sure, the Athletics were far from a playoff team or even a major league team (depending on who you ask) but it was an outstanding performance that he would double down on two starts later against the Tigers, where he pitched to another game score of 74 and kept Detroit scoreless over seven innings.

Miller, like Kirby and Gilbert, depends mostly on his exceptional control to stand out above the rest. His walk rate of 4.8% was in the 95th percentile and allowed him to make up for below-average hard contact figures. He's been adding a splitter in the offseason so the sky's the limit for this young arm.

Bryan Woo - Aug 28th vs. OAK (6.0 IP, 3 H, 0 ER, 1 BB, 5 K)

Game Score: 70

Similar to Miller, he made a big jump from Double A to the majors, although his 2.05 ERA on the Arkansas Travelers over 44 innings gave fans high hopes. Woo mostly delivered and crucially had his crowning moment late into Seattle's playoff push.

With five strikeouts and nine swings and misses, he helped lead the Mariners a 7-0 win over Oakland. His four-seam fastball almost touched 97.0 mph but mostly sat in the 94.0 mph range. He also used a cutter that was quite a bit slower and almost doubled as an off-speed pitch, hovering around the 85.0 mph mark.

He has great fastballs but a limited breaking ball arsenal, with his slider and changeup both accumulating negative run values. He threw the changeup just 52 times so he may seek to make further adjustments to his arsenal for the future.

Woo has been touted as a possible trade asset and he'd undoubtedly be valuable to many teams in baseball. Whether the Mariners choose to keep him or hock him in exchange for some improved bats, he'll be a major contributor to the team's success in the upcoming year.