The Nationals would not be here today without Patrick Corbin.

In a season with many ups and downs — really, just one “down” and then one much larger “up” — Corbin was a consistent arm in the Nationals’ rotation, especially as the ace of the staff, Max Scherzer, dealt with injuries in the second half and relative (by his standards) ineffectiveness upon his return. He was not the only rock — Stephen Strasburg was also superb — but he was the new rock, the highlight of the Nationals’ offseason, their prized signing.

On December 4, the Nationals inked Corbin to a six-year, $140 million deal, the largest contract given to any starting pitcher the entire offseason. With one full season in the books, it’s clear that Corbin has come to Washington exactly as advertised. As their third ace, Corbin’s presence in the rotation helped put them over the top. A team with three of the best 13 pitchers in baseball likely won’t stay defeated for long, and the Nationals overcame a horrid 19-31 start to win 93 games and clinch the top NL Wild Card spot.

Of course, this turnaround is not solely due to Corbin’s contributions, but having him in the rotation certainly didn’t hurt. He pitched 202 innings this year to the tune of a 3.25 ERA, 3.49 FIP, and 4.8 WAR. He outpitched both Steamer’s (3.3 WAR) and ZiPS’ (3.5) preseason projections. As a result, the Nationals had the best rotation in baseball, and they hope that their top three starters will be the difference here in October:

Most WAR From Starting Pitching Rank Team WAR 1 Nationals 21.4 2 Dodgers 19.7 3 Mets 19.7 4 Astros 19.3 5 Indians 17.9

“[Corbin’s been] a great complement to our big two right-handers,” Nationals general manager Mike Rizzo told 106.7 the FAN last Wednesday, via Patrick Reddington of Federal Baseball. “We feel comfortable rolling any one of those guys out there. It’s a luxury that few teams have, and we’re lucky enough to be able to run three quality No. 1 type of starters out.”

Corbin not only gave the Nationals the statistically best rotation in baseball, he also gave them their best rotation in franchise history. Ever since they signed Scherzer in 2015, Washington’s strength has been the success of their starters, but never before have they collectively surpassed 20 WAR in a single season. The closest they came was in 2017, when Scherzer (6.4), Strasburg (5.9), Gio Gonzalez (3.8), Tanner Roark (2.8) and the rest of the supporting cast combined for 19.4 total WAR. And, if you think back hard enough, you may remember how that year ended (Justin Klugh does). Their postseason run concluded with a crazy 9-8 loss to the Cubs in Game Five of the NLDS.

Gonzalez pitched quite well in Game Two of that series, resulting in a Nationals’ 6-3 win. This is to say that while Corbin certainly is an upgrade, it might not really matter when everything is said and done. And, if things really go poorly, Corbin might not start at all, though he will be available to pitch out of relief in the NL Wild Card Game if need be.

Still, Corbin had an excellent year, continuing to rely on the pitch that earned him his big contract: the slider. Prior to 2018, Corbin had been a bland, middle-of-the-road starter, occasionally flashing brilliance. He never topped 3.3 WAR in his first five major league seasons, never striking out more than 22% or less than 18% of hitters. He struggled with injuries at times, but even when he was on the field, he was a slightly above-average starter at best. Then 2018 came, and Corbin famously began throwing his slider as his primary pitch. His strikeout rate jumped to 31%, his walk rate dropped a tick, and he became the fifth-most valuable starting pitcher in baseball.

So when the Nationals signed Corbin, they were banking on a 2018-esque season. At the time, I wrote that I was sold on Corbin and thought he would be worth his contract. One year in, and the Nationals must be pretty pleased.

Corbin has continued throwing his slider as his primary pitch, though its usage did dip by about four percentage points. It was nearly just as effective though, generating 21.3 runs of value (2018: +27.0), and 1.74 runs of value per 100 pitches (2018: +2.08). Hitters whiffed on 52% of swings, and when they did make contact, it was weak. Corbin allowed a .198 xwOBA against the pitch, putting him in the 92nd percentile in the metric. Corbin also added in an even-slower curveball this season — the pitch’s average velocity dropped from 72.5 mph to 67.9 mph year-over-year — which provided Ben Clemens a lot of joy.

In all seriousness, Corbin has clearly been a difference-maker in Washington. By Championship Win Probability Added (cWPA), Corbin increased the Nationals’ odds to win the World Series by 1.3% this season. That’s the 19th-highest mark of any starting pitcher and the second-highest on the Nationals’ staff, ranking below Strasburg (1.8%, 10th) and just above Scherzer (1.2%, 20th).

While Corbin was unquestionably impressive, calling him the sole reason why the Nationals made the playoffs is likely a bit far-fetched. The team was aided by the continued dominance of Anthony Rendon, an excellent sophomore season from Juan Soto, the quality innings from Aníbal Sánchez, the defense of Victor Robles, and of course, the midseason bullpen moves. But we shouldn’t overlook the impact that Corbin has had thus far, especially as an outside addition. The Nationals had to go out and get him, which, given baseball’s current state of affairs, is worth highlighting. Now, with our eyes turned to the postseason, Corbin hopes to have a similar positive influence on the Nationals’ playoff fortunes.

“I’ll be ready to go [on Tuesday] if my name’s called,” Corbin said following Sunday’s game. “It’s a do-or-die game, so it will be exciting.”

For a Nationals team that endured quite the rough start, it’s worth celebrating the key moves made to assist in the recovery. While there are still five years to go on the contract, it’s hard to call the Patrick Corbin signing anything but a success thus far, though his permanent impact on the Nationals’ franchise may have not yet been established.