Think about the teams in the American League wild-card race. Focus on the teams gunning for the second position. Focus further still, on their various starting rotations. They’re bad! They’re pretty much all bad. Or, if “bad” feels too cruel, we could go with “lacking.” All of them are lacking. I don’t know if the Orioles have the worst rotation in the group, but they’ve received maybe the most notice for being so thin. It’s not like it hasn’t been deserved.

Chris Tillman was supposed to be good, and his season’s been a nightmare. Ubaldo Jimenez wasn’t supposed to be nearly as good, but his season has also been terrible. Kevin Gausman has yet to make that leap people always figure he’s on the verge of making. The Orioles traded for Jeremy Hellickson when his strikeout rate was under 14%. There’s been so little, for so many months. The Orioles are in the race despite their rotation, not because of it. They’ve just been waiting for someone, anyone, to step up.

And now, Dylan Bundy is stepping up. Of the Orioles’ rotation value over the past several weeks, Bundy has accounted for almost all of it. I don’t think a pitcher can become an ace in the matter of one month. But if one could, that month would look a lot like Bundy’s August.

Bundy started five times, throwing 36 innings. He allowed nine runs, and the Orioles went 5-0. To put Bundy’s performance in context, consider the lot of qualified pitchers over the past 30 days. Out of that pool, Bundy’s tied for first in WAR. He’s second in strikeout rate, and third in K-BB%. He’s third in the rate of swings at pitches out of the zone, and he’s run the second-lowest rate of contact. Bundy couldn’t have done very much more: He got ahead in counts, and he put hitters away, without letting them pepper the field with line drives. Bundy’s one-hitter against the Mariners on Tuesday stands as one of the better efforts in the history of the Orioles franchise.

Bundy’s case is complicated. Because of all the time he’s missed, you want to wait to totally buy in. You want to wait for him to prove himself. Because of how his innings total is climbing, you additionally want to be cautious. You hope the Orioles don’t ride him too hard. But then you have the matter of Bundy’s pedigree. He was drafted so high, and the talent’s still there. You want to think that he can do it. You look for reasons to think he’s breaking out.

Exactly what Bundy is up to, I’m not sure. He’ll need to rattle off some more starts, once hitters start to get a sense of his game plan. But this has certainly been a new version of good Bundy. Good Bundy has teased in the past, but August was an entire month of success.

As explanations go, comfort could be part of it. Bundy is just getting more and more familiar with big-league opponents. And then there’s the fact he’s been rested; Bundy made just one of his five starts on four days’ rest, a break which is fairly standard. Bundy might be feeling increasingly confident and refreshed, and those would be easy to link to performance. A rested Bundy could be a happy Bundy. Maybe that’s all it is.

But I do think there’s a little bit more. Maybe I’m just looking for things, I don’t know, but consider Bundy’s monthly splits:

Bundy, in August, was good against righties. Bundy, in August, was great against lefties, relative to his earlier performance. He’s a five-pitch pitcher, and on the year, his changeup has rated out well, with a strongly positive value. But I want to focus on two weapons: Bundy’s slider, and his four-seam fastball.

The slider is the pitch the Orioles didn’t let Bundy throw before. So when he unveiled it when this season began, observers got excited. It was possibly his best pitch in the minor leagues, and evaluators wanted to know how it could play in the bigs. For months, I think Bundy’s slider was fine, without being dominant. Through July, it got about 22% whiffs. That rate was above-average, but nothing exceptional. Then August happened. In August, Bundy’s slider got 34% whiffs. Here are August’s highest slider whiff rates, for starters who threw at least 50 pitches:

Bundy’s slider was better than ever. Just look at how he put away Danny Valencia to close out his latest gem:

The slider itself didn’t change. Bundy didn’t even markedly change how he tried to use it. He just executed the slider with a greater frequency. That’s all good pitching is. Every pitcher can throw a good pitch, from among his pitch types. The best pitchers make the fewest mistakes. Bundy spent a month making fewer slider mistakes, and if that’s development that sticks, that’s going to be an issue for opponents.

But there’s also the four-seam fastball. Refer back to the plot of K-BB% splits. Bundy upped his slider usage in August, and that helped him against righties. Yet he also unlocked a certain something against lefties. It’s time for me to borrow from Baseball Savant, because I think there was a tweak. Below, two heat maps, for Bundy throwing four-seamers to lefties. The views are from the catcher’s perspective.

Recently, Bundy has used the heat to try to jam lefties up and in. Here’s what that looks like in a game situation:

Bundy never avoided the up-and-in quadrant entirely, but in August he went there more and more. It takes a certain amount of command and confidence for a righty to pitch lefties inside like that, and that might’ve left Bundy in control of nearly every area. Four-seamer up and in, slider down and in, two-seamer and curveball away, changeup down and away. The high-and-tight fastball can change how hitters approach an at-bat, because they don’t know where to look. It’s not so much a dominant pitch on its own, but it can make every pitch more effective. Bundy has been able to locate that pitch, and it’s set up his other weapons. Lefties were forced to flail like never before.

Whether it’s all because Bundy was more rested, I couldn’t tell you. And there should still be some amount of caution here, given Bundy’s increasing workload. The Orioles know they can’t just squeeze Bundy here for every last drop. But this is something to build on. This is the latest potential flash of Dylan Bundy’s developing ace-hood. Perhaps he’s not there just quite yet. But if Bundy gets there one day, he’s going to look like how he’s looked lately. The Orioles’ rotation needed a savior, and Bundy emerged, just like how they always had it drawn up.