A version of this story was originally published in September.

Free-agent starter Blake Snell just put together one of the most bizarrely dominant and statistically extreme seasons by any pitcher in MLB history, and it earned him the 2023 National League Cy Young Award.

On one hand, Snell led the Majors with a 2.25 ERA, a .180 opponents' batting average and a .579 OPS against, and had 234 strikeouts in 180 innings, which was more than enough to qualify as one of the game's best pitchers. At the same time, Snell was also the MLB leader with 99 walks and nearly became the first pitcher since 2012 with 100-plus walks in a season.

Nobody doubts that Snell was an extremely effective pitcher this season. What is in question is how good he actually was and how Snell was able to outperform every indicator of what his ERA should be.

Here’s a look at just how unusual his 2023 season was and how he was able to pull it off.

The unicorn season

There are plenty of ways to show how unique Snell's 2023 season was, but these are some of the standout metrics:

• Snell is the first AL/NL pitcher since 1913 -- when earned runs became official in both leagues -- to lead the Majors in both ERA and walks. Snell had a 38-point advantage in ERA over Gerrit Cole while he walked 16 more batters than the next-closest pitchers (Charlie Morton and Johan Oviedo).
• Snell had a whopping 13.3% walk rate, making this one of 173 seasons in MLB history in which a pitcher had a walk rate above 13% in 150 or more innings. Snell’s 182 ERA+ was the best of all those seasons, besting Hal Newhouser's 162 ERA+ in the 1942 season.
• With 99 walks, Snell finished just one walk short of becoming the second pitcher ever -- and first since Sam McDowell in 1966 -- with 200 or more strikeouts and 100-plus walks across fewer than 200 innings in a season.
• By winning the Cy Young Award, Snell became the first pitcher since Early Wynn in 1959 to lead the Majors in walks while winning the award.

The common denominator in Snell's funky season is the walk total. It's just extremely difficult to allow that many free passes and still find this level of success. Even some of the extreme examples similar to Snell -- like Nolan Ryan and Bob Feller -- never led the Majors in both ERA and walks in the same season. For Snell, those walks are just a part of his profile, which was seemingly been embraced by the lefty and the Padres this year.

In a story from MLB.com's Padres beat reporter, AJ Cassavell, Snell and the Padres all but confirmed this idea that his high walks total is OK.

"I've got a guy here that has stuff. The message is: Go get outs. It's not: Don't walk people," Padres pitching coach Ruben Niebla told Cassavell. "Walks are part of the game, and you have the stuff to be able to pitch through walks."

Snell seconded this notion and even talked about a belief in "good walks" vs. "bad walks." Rather than give in to hitters and throw hittable pitches, Snell was comfortable walking a batter and working his way out of trouble. While this isn't a sound game plan for most pitchers, Snell isn't exactly like most pitchers.

How to win with walks

Snell made this high-strikeout, high-walk profile work because he was one of the most unhittable pitchers this season. In the pitch-tracking era (since 2008), only Spencer Strider (2023) generated a higher single-season whiff rate -- the percentage of swings that result in a miss -- in a single season than Snell this year.

Highest whiff rate in a single season, SP, pitch-tracking era
Min. 150 innings

1. Spencer Strider (ATL), 2023: 38.6%
2. Blake Snell (SD), 2023: 37.4%
3-T. Corbin Burnes (MIL), 2021: 37.3%
3-T. Gerrit Cole (HOU), 2019: 37.3%
5. Luis Castillo (CIN), 2019: 35.7%

Part of his ability to miss bats was due to the fact that he's a 6-foot-4 lefty who throws a mid-90's fastball. It's the trio of secondary pitches, though, that did the heavy lifting in generating boatloads of whiffs. Like many other pitchers of his era, Snell opted to use his best pitches more often. For the first time in his career, his fastball rate dipped under 50% this season, which led to Snell throwing his elite secondary offerings more than half of the time.

Snell's curveball was his most utilized secondary pitch (19.8%) for the first time since his 2018 AL Cy Young Award-winning season and was one of baseball's best pitches. His curveball produced an elite 56.3% whiff rate, second among individual pitches by a starting pitcher (min. 150 swings) behind only Kodai Senga's forkball (59.5%).

Additionally, Snell's curve was the fourth-most valuable breaking ball or offspeed pitch according to run value -- the run impact of an event based on the runners on base, outs, ball and strike count. In 175 plate appearances ending on the curve, opposing hitters had just 13 hits and a .140 SLG.

As if a mid-90's heater and elite curveball weren't enough, Snell also mixed in a spectacular changeup and slider. Both pitches were not too far behind in terms of bat-missing ability and overall dominance. Snell's changeup had the 14th-highest whiff rate (46.8%) among individual pitch types by a starting pitcher (min. 100 swings) and was third behind only Shane McClanahan and Tarik Skubal's changeups. His slider, meanwhile, had a 53.6% whiff rate that trailed only four pitches, including his own curveball.

When you combine the overall excellence of his non-fastballs, Snell produced one of the most dominant seasons on breaking balls and offspeed pitches by a starting pitcher in recent memory. He had a combined 51.9% whiff rate on his non-fastballs, the second-best single-season rate by a pitcher behind only Strider, who had a 53.7% whiff rate on his slider and changeup this year.

When you're simply preventing hitters from making contact against you, that goes a long way toward making this profile work.

Pitching well when it matters

This is where Snell's season gets even more interesting. Based on many ERA indicators -- whether it's expected ERA (3.77), FIP (3.44) or expected FIP (3.62) -- Snell outperformed his underlying numbers by over a full run. That's what you'd expect from a guy who walked 13.3% of the hitters he faced. Unsurprisingly, Snell's high-walk, high-whiff profile and minuscule ERA were also backed by incredible numbers with runners on base and in scoring position.

When runners got on base, Snell stranded them 86.7% of the time -- tied for the 7th-best mark by a starting pitcher in a single season (min. 150 innings) since 1901. What works in Snell's favor is many of the seasons near him were some of the best pitching performances in MLB history, such as Bob Gibson's 1968 season, Dwight Gooden circa 1985 and Pedro Martinez's 2000 season. Also ahead of him on this list? Snell's first Cy Young Award-winning season, in 2018 (88%).

That last point is especially important in this context. One might look at Snell's .470 OPS allowed with runners in scoring position this year -- third-best among all pitchers -- and simply write it off as luck. Except that Snell was even better with RISP in 2018. His .374 OPS allowed with RISP in 2018 is the third-lowest single-season mark by a starter dating back to 1901. This raises the question: Is this a skill or random noise?

It might be a little bit of both. Snell owns a career .635 OPS allowed with RISP, which is tied for 38th all-time among starters (min. 100 starts) who've faced at least 500 batters with RISP. He also had a .186 expected BA with RISP this season, giving him further support that he really is pitching better in these situations.

At the same time, half of Snell's eight MLB seasons have seen him allow an OPS north of .700 with RISP. Situational pitching -- and the small samples that come with it -- tend to have wild year-to-year fluctuation. Good pitchers like Snell, however, tend to find themselves pitching out of jams.

It's also notable that Snell was the benefactor of great defense behind him this season. When it comes to good batted-ball luck, having strong defense tends to put more good luck on your side. While the Padres underperformed this season, their defense certainly did not.

Led by defensive stalwarts Manny Machado, Fernando Tatis Jr., Ha-Seong Kim and Trent Grisham, San Diego's defense ranked seventh or better in Outs Above Average (+26), Defensive Runs Saved (+40) and Ultimate Zone Rating (+26.2). They were especially good behind Snell, providing +8 OAA when he was on the mound, which tied for the 10th-most by any defense for an individual pitcher.

As is the case for most great seasons, there's some combination of factors that need to come together at the right time. Mostly, that’s the player performing at his best, but with that also comes at least some good fortune. Snell’s 2023 was no different.

Whatever you think of it, one thing is for sure: Snell put together a season unlike any we’ve ever seen.