Josh Hader entered Monday’s game in the bottom of the seventh inning with the Brewers clinging to a one-run lead. Nine batters and eight strikeouts later, that one-run lead was the margin of victory. Jeff Sullivan predicted this, or something like this, more than two weeks ago in his article titled “Josh Hader Is Becoming Baseball’s Most Valuable Reliever.” You can see a lot of things coming if you read Jeff’s work, as he covered Hader’s arsenal and how the Brewers lefty is carving up hitters:

If Josh Hader isn’t baseball’s most valuable reliever, he’s close. He could get there soon, elbow willing. Plain and simple, he does everything right, going multiple innings at a time and pitching well independent of batter handedness. You could think of him as peak Dellin Betances, another non-closer who racked up strikeouts over 70 or 80 or 90 innings. Betances made four consecutive All-Star Games. Maybe his control is starting to go, but nothing is forever. Hader is that good, and he’s only improved since basically doubling the size of his repertoire.

Fast-forward a couple weeks and here’s the reliever leaderboard for April.

Hader is rightfully up top. That K/9 number is incredible and the 0.42 FIP naturally follows. Maybe most interesting is that Hader is the only pitcher on the leaderboard who has given up a home run. In small samples like what we have through one month, a homer makes a pretty significant difference. The only other pitchers among the top 20 of reliever WAR with a homer allowed are Craig Kimbrel and Bud Norris. For Hader to top the list despite allowing a home run is truly remarkable. That homer, to Tommy Pham on April 11, was very nearly not a homer considering it was called a double on the field and required a review to be turned into a home run. If that ball was a few feet shorter, Hader’s FIP for the month would have been -0.30. If you were wondering if that would have been some sort of record, the answer is yes, it would have.

The table below shows the lowest monthly FIP totals since 2002 for relievers with at least 15 innings.

That one home run kept Hader behind Michael Feliz and Eric Gagne, but it still places him among the best relievers over the past 17 seasons. Baseball-Reference took a look at their monthly splits and came up with a rather impressive feat regarding Hader’s strikeout numbers.

Josh Hader is averaging 19.5 strikeouts per 9 IP. Not only would that be the best K/9 over a full season (left), it's the best K/9 ever posted in a single month (right) *min. 15 IP pic.twitter.com/ScpuU1aZ57 — Baseball Reference (@baseball_ref) May 1, 2018

In terms of strikeout percentage, nobody has topped 55% in a month with at least 15 innings since 2002, making Hader’s 63% that much more impressive. When looking at that strikeout total for the month, consider the following: Relievers, on average, have struck out 23.9% of batters this season. Hader would need to fail to strike out the next 101 batters in order for his strikeout rate to drop to the league average for a reliever.

About the game on Monday, consider this…

Josh Hader joins Ron Davis of the 1981 Yankees as the only pitchers to have an outing like this: – No more than 9 batters faced

– At least 8 strikeouts — Andrew Simon (@AndrewSimonMLB) May 1, 2018

And also this from Joe Sheehan…

Josh Hader's outing last night is the longest in baseball history (2 2/3 IP) in which every out was recorded by strikeout (eight). #brewers #mlb — Joe Sheehan (@joe_sheehan) May 1, 2018

Striking out eight of nine batters in relief is amazing, but striking out even seven of 10 is an accomplishment. According to the Baseball-Reference Play Index, it is something that’s been done only 27 times in history. Last August, Chad Green struck out seven of the eight batters he faced, giving up a hit to one and retiring one runner on a caught stealing. That’s the only time a reliever has struck out seven of eight batters faced. Striking out six of six batters is something that’s only been done seven times, the last by Alfredo Simon in 2013.

While we are focused, and rightfully so, on the strikeouts, the situation Hader faced was pretty unique. The Brewers asked Hader to finish a game with a one-run lead and eight outs to go. That just hasn’t happened very often. In baseball history, there have been 129 games where a reliever got eight outs and faced nine batters or fewer to preserve a one-run lead and close out the game. Hader’s was the first since May 18, 1992, when Kenny Rogers came on in relief of Kevin Brown and retired all eight batters he faced, including Jim Thome, Albert Belle, Carlos Baerga, Mark Whiten, and Sandy Alomar Jr.

I checked post-strike data for one-run saves on outings of at least three innings where the pitcher faced the minimum number of batters, or one over the minimum like Hader, and there were none. We see three-inning saves today, but those are mostly in blowouts. We see some two-inning saves from closers like Raisel Iglesias sometimes. We see two-plus-inning saves where the team tacks on some extra runs and, because the pitcher enters in a save situation, he can remain in the game and collect the save. We don’t see what we just saw from Josh Hader. It’s not something we saw from early fireman days, either. The 70s and 80s would have seen maybe two or three games in an entire season like the one we saw from Hader, even if we don’t include strikeouts at all.

Josh Hader concluded an incredible month with a historically great outing. All those strikeouts make it a singular performance in history, but in the past 25 years, the outing was just as rare even without the strikeouts. The Brewers lost a relief ace in Corey Knebel early in the season. While he probably can’t keep up this pace, right now, Hader is pitching enough innings for the both of them. If Knebel comes back strong for the Brewers, all leads may be safe.