One of my favorite parts of the trade deadline happened right at the deadline itself. As the deadline passed, a Mariners writer or two tweeted out that no trades had been made. Then, a few minutes later, it was announced that J.A. Happ had been traded to the Pirates. It happened suddenly, and it arguably only happened because A.J. Burnett had gotten injured. There were never any Happ rumors to speak of; the MLB Trade Rumors archive doesn’t show anything. Happ was essentially unwanted and mediocre. I forgot who he was traded for, so I looked it up, and I’ve forgotten again. Deadline additions don’t get much less sexy than this.

But sometimes the present doesn’t give a crap about the past. Since getting traded to the Blue Jays, David Price has been worth 1.8 WAR. Makes sense; he’s an ace. Since getting traded to the Pirates, J.A. Happ has been worth 1.4 WAR. Makes less sense. All the other traded starters have done worse. Johnny Cueto’s done worse. Cole Hamels has done worse. Scott Kazmir has done worse. They’ve all done worse. I just came across an article a few minutes ago suggesting that maybe Happ should start the Pirates’ wild-card game. That’s insane, but it still speaks to how shocking this has been. Happ has pitched like a valuable pitcher, after the Pirates got him for basically nothing. Baseball’ll get ya.

So you know what the next section is. The next section is: what? What is this? What do the Pirates have J.A. Happ doing? I’ll do my best to try to explain.

Maybe it would just be enough to say “Ray Searage“. He’s developed an almost bulletproof reputation, and I’m not sure there are any fans out there who have a greater degree of trust in their pitching coach. Ask a decently-invested Pirates fan, and he might just tell you it’s Searage magic. The usual. And apparently Searage has been good for Happ’s confidence. Or, maybe the good results have been good for Happ’s confidence. I’m sure he’s thrilled, too, to be pitching for a winner, but I’d like to get more specific and data-y. I’ve prepared three points, hopefully mostly explaining what the numbers say has happened.

1. More fastballs

The version of Happ the Mariners traded for had just thrown 72% fastballs for the Blue Jays. And that made sense, because Happ’s fastball just kept getting faster and faster. But the Mariners version cut back. According to our information, Happ threw 64% fastballs. According to Brooks Baseball, he threw…64% fastballs. Since joining the Pirates, he’s back up at 73%. They’re almost all four-seamers, instead of the two-seamer Happ used to play with.

Maybe a better header would’ve been “more hard pitches,” because Happ also has a slider or cutter, and he’s throwing that more than he did as a Blue Jay. The other direct effect is this: by throwing more hard pitches, Happ is throwing fewer soft pitches, including his curveball and changeup. The Pirates version of Happ has moved away from those pitches, and while they haven’t been abandoned entirely, they’ve been featured just often enough to keep the hitter honest.

When Happ was a Mariner, right-handed hitters saw hard pitches 74% of the time. Since Happ joined the Pirates, right-handed hitters have seen hard pitches 88% of the time. That’s probably not an accident, against opposite-handed bats. Happ has more often gone with his strength.

2. More strikes

Or, “more aggressiveness.” This goes hand-in-hand with the change in pitch usage. Some pitches are designed to end up out of the zone. Some pitches are designed to end up within it, or at least near it. Happ’s strike pitch has long been his fastball, so now that he’s throwing a lot of fastballs again, it follows he’s getting more strikes. Mariner Happ threw about 63% strikes, a bit below average. Pirate Happ has thrown about 67% strikes, a few points above average. Viewed differently, Mariner Happ threw just under 46% of his pitches in the zone. He was down around 44% in his final stretch. Pirate Happ has thrown 50% of his pitches in the zone. More pitches in the zone means more strikes. It means more pitcher-friendly counts. And that means hitters expanding their own zones to protect. Happ’s getting a few more chase swings, now. It all works together.

The problem with Happ’s softer pitches is that he doesn’t have great control of them. Frequently they’d end up as balls, balls too wild to swing at. Happ has tried to make those pitches better, but now he’s using them less, nibbling less, believing in his fastball and slider/cutter. Maybe it’s not easy to flip that switch in your brain, when you’re a lefty and your fastball isn’t overpowering, but Happ has to be gaining confidence. His main two pitches are doing enough.

3. More favorable opponents

I don’t mean for this to be controversial. I don’t mean to take anything away from what Happ has done. It’s just that this point can’t be ignored. Most simply, Happ has gone from the American to the National League, and the NL is believed to be a little worse. But that isn’t a very strong point. This can be made a lot stronger.

To begin, Happ faced lefties 23% of the time when he was a Mariner. Since joining the Pirates, he’s faced lefties 33% of the time, which is an awful large uptick. That’s one more lefty for every 10 batters. Happ, like everyone, will take a more common platoon advantage.

And that partially explains the following. I looked at every single batter Happ has faced on the season. The batters Happ faced as a Mariner have averaged a .322 wOBA against lefties this year. The batters Happ has faced as a Pirate have averaged a .303 wOBA against lefties this year. That’s a pretty dramatic split.

Maybe you don’t like one-year data. Good! You probably shouldn’t. The batters Happ faced as a Mariner have averaged a .329 wOBA against lefties over the past three years. The batters Happ has faced as a Pirate have averaged a .304 wOBA against lefties over the past three years. That split is even bigger. Happ, in short, has faced worse hitters. Significantly worse hitters. He’s faced more lefties, but he’s also just faced worse righties. It’s not at all like every opponent since joining the Pirates has been bad — Happ has had to deal with, say, Paul Goldschmidt — but there’s no getting around this point. When opponents are worse, performance is better. That’s always true, given enough time.

That should just about make the sense that needs to be made. And I didn’t even mention that Pirate Happ has 19 called strikeouts, after Mariner Happ racked up 21. Throw that in as a fourth and final point. J.A. Happ has pitched better since joining the Pirates. He’s been more aggressive, and if you believe some of the interviews, he feels balanced and rejuvenated. The Pirates have done well to turn him into a useful and even helpful asset. He’s not actually an ace, of course. He’s presumably benefited from a relatively soft slate of opponents. No one should start J.A. Happ over Gerrit Cole or Francisco Liriano on purpose, if Cole and Liriano are conscious and available. But, the trade deadline will surprise you. If I had to guess, I’d say it’s even surprised the Pirates.