(Photo by George Walker/Icon Sportswire)

On Wednesday, the Houston Astros set a record for the fewest runs allowed through 50 games in a season. Just 126 runners crossed the plate against Houston in those games. 2.52 runs per game. Absurd. Everyone knows how insanely good the pitching has been. The Astros starting rotation seems to mow down any challenge that dare present itself, and the bullpen has sneakily posted a 2.76 ERA to date. We could dig and find a multitude of absurdities that they achieved this year. But I would like to focus on one.

Houston’s starting rotation is comprised of four right-handed pitchers and one left-handed pitcher. Gerrit Cole, Justin Verlander, Lance McCullers, and Charlie Morton are those righties. Dallas Keuchel is that lefty. With a 3.43 ERA and 4.25 FIP, Keuchel has lagged behind his right-handed rotation mates. Yes, that is lagging behind in the current state of Houston’s pitching staff. Generally speaking, left-handed hitters possess an advantage when going up against a right-handed foe. So with the sole southpaw in Houston “struggling”, one might expect that the lefty hitters have presented a minor issue for the rotation. An issue relative to their overall performance, of course. This is not the case. Not the case at all, It’s quite the opposite, actually.

In terms of weighted on-base average allowed (wOBA) against right-handed hitters, two Astros starters sit near the top of the leaderboard. Verlander ranks 4th, and Cole ranks 12th. You have to go a little farther down to find the other Houston starters. But in terms of wOBA allowed against left-handed hitters, four members of the rotation sit in the top-21. None of them are Keuchel. Houston’s righties have surrendered a wOBA of .216 to lefties and a wOBA of .252 to righties. Reverse-splits are no anomaly to baseball. It happens. But stuff like this shouldn’t happen. It defies baseball logic that four right-handed pitchers are collectively performing significantly better against their opposite handed opponents. It’s absurd. It’s weird. And like many other things Houston is doing, it’s historic.

Going back to 1999, I found the wOBA allowed to left-handed hitters from right-handed starters for each major league team. Plotted is that wOBA figure for each team in each season:

It’s pretty easy to find the Astros. They are that blue dot in 2018 that’s far lower than any other point on this graph. In 2011, the San Francisco Giants’ righty starters surrendered a .276 wOBA to lefties. That is the single lowest figure aside from Houston’s .216 from this season. Verlander, Cole, McCullers, and Morton are dominating righties, but they are putting away lefties in an unimaginable way.

Let’s look at each pitcher’s past performance against each hitter handedness. Here is the difference in wOBA against lefties/righties for 2017 and 2018. Positive means they performed better against lefties.

McCullers and Morton are doing what they did last year. Despite their handedness, they absolutely dominated lefties. Significantly more so than righties. For Verlander and Cole, though, the difference is not so typical. How are they putting together this success as a group?

All the signs of lefty dominance point to their breaking balls. McCullers is the curveball god, and his struggles to “feel” for the pitch may conclude his lesser success against lefties this year. Morton has a lesser-known yet devastating curveball. Verlander and Cole both possess slider and curveball combos that have produced immense success. Examine the results of each pitcher’s breaking pitches against lefties this season:

Player Usage Swing% Contact% wOBA Verlander 32% 40.1% 58.1% .267 Cole 41% 46.5% 54.7% .283 McCullers 52% 50.6% 65.7% .209 Morton 39% 41.2% 38.2% .102 League Average 23.1% 42.9% 70.6% .269

All four utilize their breaking pitches against lefties significantly more than the league average and generate swings right at or above league average. Where this group really sets itself apart, though, is missing bats. Aside from McCullers, the contact rate for each pitcher on their breaking balls is far below league average. When lefties swing at Charlie Morton‘s curveball, they make contact less than 40% of the time….40%. How? That alone is incredible, but Morton’s pitch is just sitting at the top of an otherwise amazing group of breaking balls.

An amazing group of breaking balls from an amazing group of pitchers doing many amazing things. The Astros pitchers are breaking records and achieving unfathomable things. Including what they have done to left-handed hitters despite their lack of success from southpaw pitchers.