It’s halfway through May and the Washington Nationals are still flirting with a .500 season. Patrick Corbin hasn’t been the worst starter in baseball. Life is good.

Corbin has received much criticism of late. After his remarkable 2019 regular and postseason, Corbin has declined severely. Last season, he was one of, if not the worst pitchers in all of baseball.

So what has changed? Over the past three seasons, he’s drastically changed his pitch mix, including briefly adding a cutter. This season, Corbin has simplified things, throwing only four pitches.

So far in 2023, Corbin has become a sinker-slider pitcher, throwing those two pitches 80.8% of the time. This move makes sense, as the four-seam was the worse performer compared to the sinker last season. The move has worked so far, with Corbin posting better results this season.

A key statistic to watch is how often the sinker is being put in play. He is getting whiffs just 7% of the time on the pitch, and getting strikeouts just 8.1% of the time. This is not always a bad thing. Pitchers can find success by getting only a few whiffs and a lot of weak contact on the ground.

Except so far this season Corbin has a .552 expected slugging against his sinker, the 35th highest of the 220 sinkers that qualify. Last season, only three qualified hitters finished with a slugging percentage higher than .552. Aaron Judge, Yordan Alvarez, and Paul Goldschmidt.

His slider on the other hand has had more success. One of the big changes that we have seen this year is Corbin’s velocity. It’s dropped across the board, and the results are best seen in the way his patented slider has been playing. This decreased velocity has given the slider an additional 4.3 inches of drop. That is enough to take it from below average in that respect to above average, if only by a little bit. While that change likely isn’t much of a mechanical adjustment by him, it means that the slider plays a bit better than sliders at a similar velocity.

Because of this, the slider has been an above-average pitch. He goes from having four and a half bad pitches (because his curveball was not really a pitch and was a waste pitch) to one good one and three bad.

The issue is that this slider is over-performing expected metrics. Now those metrics are not the end all be all since last year he underperformed those same metrics. Those expected metrics from last year are still worse than this season so the quality of pitching we have seen from Corbin has improved.

Corbin has also taken a massive step forward in his approach. A few weeks ago I talked about how crucial Mason Thompson’s new strike-throwing approach has helped him, and this same change has helped Corbin. Last season, Corbin walked 2.89 batters per nine innings. So far he has cut that rate by more than a whole batter to 1.79 BB/9. He has upped his zone rate to 52.6%, a 4.3-point increase from last year.

It’s as simple as when he gets ahead, he dominates. When he starts the at-bat down 1-0, he allows hitters to hit .333/.392/.500. When he starts 0-1, hitters hit .275/.292/394.

Part of the issue is Corbin’s pitches are too discernible. He fails to get chases and whiffs with his slider to the point where the pitch is best when it is in the zone. His changeup is left in a similar situation, where he only really finds success in the edge of the zone. This leaves Corbin in a rough place.

So how do we fix it? First and foremost, Corbin lost his slider. Between 2019 and now, the primary difference between the slider is its spin rate and velocity. Thankfully, his performance versus left-handed batters hasn’t decreased nearly as much as it has versus right-handed hitters, so let’s focus on the righties.

When comparing locations against righties in 2019 and 2023, you begin to see the issue.

Where he is attacking hitters has completely changed. He has moved too high up against hitters, something a pitcher of his skill set absolutely cannot do. Corbin has to live down in the zone and attack hitters horizontally, attacking righties outside with his sinker and then living down and in with his slider. This could either be an approach issue by Corbin and the Nationals front office, or he could simply have lost control. You’d hope it is the former.

The main thing that would help Corbin is reintroducing the cutter. While the one he threw eight times in 2021 is a good jumping-off point, it could use some work. This cutter would bridge the gap between his four-seam and his slider.

His cutter in 2021 had ideal vertical movement, having 11.5 inches of separation from his four-seam and 13.4 inches from his slider. Corbin just did not have the horizontal movement he needed. While he does not need a ton of movement in that department, it certainly needed more than 1.5 inches. This pitch would allow him to attack righties on the inside edge, and then work away with his sinker, and finally drop the slider below the zone.

We’ve seen with our own eyes what adding a cutter can do to an arsenal with Corbin’s teammate Josiah Gray. He went from allowing 2.3 HR/9 to 0.85. A massive jump for the young pitcher. Control is still an issue for Gray, but simply denying home runs has turned Gray into an above-average arm.

Hopefully, for the Nationals' sake, Corbin can continue to turn around. If he can pitch his way into being traded for a prospect, that is an absolute win for the Nationals considering what he has been since the World Series title.