Before the start of the year, the Padres’ starting rotation was the butt of so many jokes. They essentially had to build it out through free agency, but not even through the appealing parts of free agency. More like the Jered Weaver parts. Here and there, there was occasional speculation the Padres could go on to have one of the worse rotations in recent memory. At the same time, people held the Cubs in the conversation for having maybe the best rotation around. It was certainly one of the best a season ago. Why would anything change? Cubs good. Padres bad. These statements were inarguable.

We’ve completed just a sixth or so of the season. You should be sticking to many of your preseason thoughts. But let me just show six numbers. Here’s how the Cubs’ rotation has done:

ERA-: 109

109 FIP-: 109

109 xFIP-: 94

And here’s how the Padres’ rotation has done:

ERA-: 106

106 FIP-: 106

106 xFIP-: 95

The Padres are basically right in the middle in WAR. It’s been a mixed bag of results, but overall it’s been fine, even slightly more effective than the Cubs. It’s a strange place for us to be, and surprising group effectiveness is driven by surprising individuals. Trevor Cahill has earned a front-page post.

Cahill is one of three Padres starters signed to basically identical one-year contracts worth $1.75 million. Cahill was a starter with the A’s, and then he became a starter with the Diamondbacks, but then he became a reliever with the Diamondbacks, and his career changed course. Cahill mostly relieved in 2015. He mostly relieved in 2016. The Padres brought him in to start again, and although he’s done that only five times, this is a fairly telling table:

Trevor Cahill, Starting Season IP K-BB% 2009 178.2 2% 2010 196.2 7% 2011 207.2 7% 2012 200.0 10% 2013 142.2 6% 2014 87.0 9% 2015 12.1 -3% 2016 5.0 6% 2017 30.0 21%

Cahill is still turning out plenty of grounders. But he’s also missing bats like never before, which I don’t think anyone was counting on as he shifted back to longer appearances. This isn’t a situation where Cahill has suddenly added velocity. It doesn’t even seem like a situation where Cahill has added a brand-new pitch. He’s just…better, better with his repertoire, and here’s a plot I decided to make, showing frequency of plate appearances getting to two strikes, and also the frequency of those two-strike plate appearances resulting in strikeouts. Cahill’s the blue dot.

The Cahill point doesn’t stand out. No one’s trying to make the argument that Cahill is a singular freak, or the very best pitcher around. But Cahill ranks in the upper sixth in getting to two strikes. He also ranks eighth in turning those two-strike counts into strikeouts. Both rates for Cahill are very easily career highs. Similar pitchers this season include Michael Pineda, Jacob deGrom, and Lance McCullers.

Out of all 135 guys with at least 20 innings under their belt, Cahill’s 10th in strikeout rate. He’s seventh in contact rate, and eighth in adjusted xFIP, between Clayton Kershaw and James Paxton. For a clue of how this is happening, you needn’t look much beyond Cahill’s plate-discipline numbers. How have hitters handled themselves with Cahill on the mound? Here is the key to basically everything:

Only five pitchers have gotten a greater rate of swings at pitches out of the strike zone. That’s good. No pitcher has gotten a lower rate of swings at pitches inside the strike zone. That’s also good! The difference between the two rates, for Cahill, is 12 points. That’s more than eight points better than the next-closest point. Cahill, in a way, is doing what Andrew Miller has done: He’s made hitters aggressive at all the wrong pitches.

There’s no one perfect, all-encompassing explanation, but here’s something that goes a long way. Cahill has a sinker. He also has a slider and a changeup. But here’s how he’s used his curveball:

More curveballs this year than ever before. And now here’s how the curveball has done:

Also more whiffs than ever before. More whiffs, despite an increase in frequency. When hitters have offered at Cahill’s curve, they’ve missed the ball more than half of the time. It’s a dangerous breaking ball, and Cahill’s used it to great effect.

Hitters have swung at Cahill’s curve more than ever. They’re making their worst rate of contact. When Cahill’s thrown a curve in the zone, hitters have swung 43% of the time. When Cahill’s thrown a curve out of the zone, hitters have swung 46% of the time. You’ll recognize how sloppy that makes the hitters look. Cahill’s just had that curve working, and here you can see Nolan Arenado not really know what to do:

Curveball, surprising called strike. Later in the game, Cahill weaponized the pitch for a punch-out:

There’s another key buried in there. I mentioned that Cahill is better about getting to two strikes. That’s a function of a handful of things. But with two strikes — maybe that’s where the biggest adjustment has been made. Last year, with two strikes, Cahill threw 12% curveballs. For his career, with two strikes, he’d never before exceeded 20% curveballs. This year, with two strikes, Cahill’s thrown 43% curveballs. It’s become easily his preferred putaway pitch, taking the place of the changeup, and hitters have had a devil of a time. For five starts, Cahill has had that curveball working. Promising results have been closely linked.

It’s never been easy to trust Cahill as a strike-thrower. It’s because he’s never thrown that many strikes. Even now, it’s not like he’s constantly getting ahead. But he has the best curve he’s had in his life, and the sinker hasn’t betrayed him. The slider and changeup are there to keep hitters honest, and so we have a legitimately good Trevor Cahill to consider. Through the season’s first month, Cahill has warped his opponents’ collective sense of the strike zone. Should that continue, the Padres’ rotation will keep on over-achieving. And Cahill himself will become a popular conversation topic in July.