The A’s don’t currently occupy a wild-card slot, and, even if they did, it’s May 22, which is too early to be talking about wild-card slots. That said, the A’s have won four in a row, and the A’s are three games over .500. While they’re in fourth place in their own division, that’s mostly because their own division is strong.

Back in the spring, I bought into Oakland’s wild-card hype. There’s no question, though, their odds were hurt considerably by the injuries to Jharel Cotton and A.J. Puk. What was left was a short-handed pitching staff, a staff that would need a few players to step up. One of those players has been Daniel Mengden. And honestly, if you want to understand why the A’s are where they are, you have to give much of the credit to the offense, an offense that seems to come in waves, an offense that’s been among the best in baseball since last July. Yet moving back to the pitching staff, Blake Treinen has been a revelation. He’s pitching like one of the better relievers in either league, and he’s tied with Josh Hader for the most saves lasting more than one inning.

As unsettled as the A’s pitching staff might seem at the start, they at least have an answer at the end. Treinen is finally fulfilling his potential, having come to Oakland as something of a major-league prospect.

Treinen will turn 30 years old in a handful of weeks. He was traded from the Nationals to the A’s last July, in what was his fourth big-league season. The Nationals didn’t need Treinen anymore, because he frustrated them, and because they were adding both Sean Doolittle and Ryan Madson. From the A’s side, they were ecstatic to pick up prospect Jesus Luzardo, but they saw something in Treinen at the time. Treinen wasn’t a prospect in the classic sense. He was a guy who’d immediately be added to the roster. Teams out of the race don’t usually trade relievers for relievers, but now you can understand Oakland’s thinking. They knew then they weren’t terribly far off, and Treinen is doing exactly what they wanted.

It’s not as if Treinen was ever awful. The differences between Treinen now and Treinen then are subtle. But this table is useful; here’s Treinen over the year before the trade to Oakland, and over the near-year since the trade to Oakland.

Blake Treinen, Pre- and Post-Trade Split IP K% BB% ERA- FIP- O-Swing% Contact% Mid-2016 to Mid-2017 69.0 21% 10% 96 83 35% 76% Mid-2017 to Present 60.2 27% 8% 42 65 41% 69%

Treinen has improved a little bit virtually everywhere you look. He’s improved his ability to throw strikes, and he’s improved his ability to keep his sinker down. He’s getting a little bit more sink than he used to across the board, and to the eye he just looks mechanically smoother. He’s also continued to develop. Since the 2017 All-Star break, Treinen is fifth among relievers in innings and fifth in ERA, while ranking ninth in xFIP. Since the start of this season alone, Treinen has a top-five reliever WAR, a top-five chase rate, and a top-ten contact rate. Treinen, last year, put it together down the stretch. Now he’s just doing it all in the spotlight.

When the A’s acquired Treinen, he already had that signature sinker. The one in the upper 90s, the one that resembled a right-handed version of the Zach Britton deathball. Here is the sinker:

Treinen, also, already had a sharp slider. It’s a swing-and-miss slider, as many sliders are:

Yet as Treinen has emerged, he’s also started to give hitters a new look. The changeup he flirted with is gone. The new thing isn’t always so evident to the eye. On TV, it just resembles the sinker. But I want to show you a couple plots from Texas Leaguers, showing pitch movement. On the left, 2017; on the right, 2018.

You see four-seamers and sinkers in both plots, but, on the right, something about the four-seamers has changed. There’s a greater differentiation between the pitches, with the four-seamers getting considerably less horizontal movement. In this case, less horizontal movement is a good thing, because it allows the fastballs to separate. You can also see this in a movement plot from Brooks Baseball:

The sinker is still the sinker. It’s still incredibly fast, and it still dives in on right-handed ankles. But the four-seamer looks like more of a true four-seamer. Or maybe it’s just that Treinen is actually throwing a four-seamer now, and before people were just misclassifying certain sinkers. How can I be so confident that the four-seam fastball here matters? Because, conveniently, he just said this to Susan Slusser!

Just as important this season, Treinen argues, is his four-seam fastball, a pitch that A’s minor-league instructor Gil Patterson first suggested to him when Treinen was drafted. He got away from throwing the pitch, however, until a month before he was traded back to Oakland. “It’s definitely helped,” he said.

Traded back to Oakland. That’s another part of this story. The A’s drafted Treinen in the seventh round in 2011, and then, in 2013, he went away, part of a three-team exchange that brought the A’s John Jaso. Perhaps the A’s reacquired Treinen in part because they wanted to get back what they’d lost. No matter; Treinen is back with his original organization, and he’s thriving. Here’s a look at the new old four-seamer:

Again, it might not look that special. It might not look meaningfully different from the sinker. But put yourself in Trey Mancini’s shoes. With the count 2-and-2, you know you have to protect. You know Treinen throws hard. The fastball comes out of his hand, and it looks like it’ll catch the outer edge. You think it’s a back-door sinker, so you swing. Instead, however, it’s a four-seamer away off the plate, with five or six fewer inches of horizontal movement. The pitch wasn’t going to catch the plate at all, but it’s all about exploiting that uncertainty. Treinen is still going sinker-first, because the sinker is terrific, but the four-seamer helps keep hitters off of the sinker, which helps keep hitters off of the slider. Everything works together, and, for Blake Treinen in 2018, everything works, period.

When you throw strikes, miss bats, and get grounders, you’re doing everything any pitcher needs to be able to do. Blake Treinen has replaced Sean Doolittle by pitching pretty much as well as Sean Doolittle, and there are few bigger reasons why the early-season A’s have been competitive. It’s unlikely the pitching staff will ever become a strength. This is a team that’s going to be driven by its offense. But even a mediocre pitching staff can lean on its strengths. Treinen is ready for the workload.