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.

Logan Gilbert - August 8th vs. SDP (7.0 IP, 1 H, 0 ER, 0 BB, 12 K)

Game Score: 87

For those who have been around since his debut in 2021, you already know that Logan Gilbert profiles as a pitcher with a great four-seam fastball whose Achilles heel is his tendency to give up hard contact a little too frequently. On the upside, when Gilbert is at his best, his mastery of the strike zone can have devastating results for the opposing team.

Against the San Diego Padres, Gilbert was incredible, fanning 12 batters over seven innings and garnering 15 swings and misses. His four-seam fastball sat close to 97 mph and he used the pitch to cut up the Padres lineup without mercy. To make matters worse, on 20 sliders thrown, Gilbert gave up just one ball and one hit.

While his cumulative 2023 ERA of 3.73 was slightly worse than his 2022 ERA of 3.20, his peak performance in 2023 was much higher. Much of the change can be chalked up to a slight dip in potency for his four-seam fastball. While had run values of 19 and 12 on the pitch in 2021 and 2022 respectively, it had a run value of 0 in 2023. Instead, his slider run value of 15 made that the most lethal weapon in his five-pitch arsenal. If he's able to put two and two together, Gilbert's going to have a career year in 2024.

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.