Bud Black pitched twice in Denver.

The first occasion was as a minor leaguer for the Omaha Royals in 1983 when he faced the Denver Bears, the Triple-A affiliate of the Texas Rangers. A decade later, Black returned to Mile High Stadium at the foot of the Rocky Mountains for his first and only major-league start at 5,200 feet above sea level — in this case, against the expansion Rockies on May 12, 1993. The next closest stadium in elevation at the time was Atlanta’s Fulton County Stadium (1,050 feet) followed by Kauffman Stadium in Kansas City (886 feet). Perhaps in all of professional baseball only Mexico City’s Foro Sol (elevation: 7,350 feet) was an environment less conducive to pitching.

Even as a minor leaguer in the early 1980s, Black had heard all about the perils of pitching in the thin air of Denver, about what it means to have fewer molecules bouncing off batted balls and pitches. Most often Black heard about how ineffective breaking pitches were there, with the Magnus force exerting less influence over a ball due to an air density of just 82% compared to sea level.

“I heard that. I tested that theory on my own,” Black told FanGraphs. “I placed a high degree of focus on the games I did pitch there, granted there were only two [starts]… When I threw a curveball, I had to throw it properly. I had to throw it with good spin. My release point had to be on… I had to release it at a certain point. Granted, that is a challenge.”

Mile High Stadium was a terrifying place. With a 365-foot power alley in left-center, even Eric Young could power up.

After struggling early in his only major-league start in Denver, Black finished by retiring 21 of 22 batters before roughly 50,000 fans — a start he discussed with the Denver Post this offseason after he’d been hired as the Rockies manager. It was, in part, through that firsthand experience that his approach to pitching at altitude was informed. The competitive 36-year-old Black wanted to beat not only the Rockies, but also the environment. He wanted to test, and prove wrong, conventional wisdom. It was his experience there that has shaped some of philosophy about pitching at Coors Field. He thought he could throw, and trust, his breaking ball there.

Black wanted to test theories about pitching at altitude and as a player. He thought about it some with the San Diego Padres earlier in his managerial carer. But upon being hired as the Rockies’ new manager in November, he had the opportunity to experiment in the games’s most difficult environment, the sport’s most challenging laboratory.

Said Rockies pitching coach Steve Foster, who Black retained — and who believes in the curveball — of coaching at Coors Field: “It’s the ultimate challenge.”

Plenty of executives, coaches, and pitchers have failed to conquer the challenge, to unlock the secret of pitching in Denver. The Rockies have tried four-man rotations, to collect sinkerball pitchers, to bring in big-money, top-of-the-rotation arms. Little has worked. But anyone capable of succeeding in Coors will be remembered. And these Rockies might have figured out how to pitch, and win, at altitude. After having never produced an ERA- better than 90 for a season (the metric adjusts for ballpark and run-scoring environment), the Rockies enjoyed a franchise-best mark entering the weekend, pacing the club to its 43-26 start.

By adjusting their sights, by adjusting their pitch mix — and certainly by adding considerable talent — the Rockies have perhaps cracked the code in pitching at Coors.

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Prior to the spring, Black had found an ally in the breaking-balls-can-work-at-Coors camp in bullpen coach Darren Holmes, whom Black also retained along with Foster. Holmes pitched in Denver for a number of years and often successfully. He was hired in part for his forward-thinking application of biomechanics. He was also non-traditional in that he encouraged his pitchers to throw curveballs. After all, Holmes threw his curveball there and often had success.

“[Trust in the breaking ball] was reiterated from [Holmes],” Black said. “He had a good breaking ball. A true 12-6 breaking ball.”

When Black, Holmes, and Foster and met with individual pitchers this spring in Arizona they were also making a sales pitch: they were selling the curveball to those who had one but lost trust in it. They were selling the pitch to those whom they thought could benefit by throwing it, from its velocity separation and depth.

They asked Tyler Chatwood to bring the pitch back after shelving it. Now, Chatwood is throwing curves at an 11.3% rate, compared to 4.8% last season. They have asked Chad Bettis to spike his curveball usage — which dropped by five percentage points last season — after he builds up enough stamina following his cancer treatment. Foster and Holmes had already worked on developing a curveball for Jon Gray, who had never thrown one. Gray threw his curve at a 10% rate last season and again threw it at a 10% rate this season before injuring his foot. German Marquez is throwing the pitch on a quarter of his offerings.

Beyond throwing the pitch, the Rockies’ staff wanted their pitchers to focus on where they threw the pitch.

“I’ve heard [Holmes] talk to a lot of our young pitchers, it’s more about your sight line,” Black said. “Every pitcher has a different visual of what they look at when they throw their breaking balls. Some guys look at the catcher’s pads, look at the umpire, look at something off the hitter. Some guys visualize the pitch out of their hand and landing it in a [certain area]. Darren thought for him, and kind of used it as a coaching tool, that if you’re a guy that throws your breaking ball to top of the catcher’s head, lower your sights and try to throw it to his chest. That’s sort of the mindset behind the teaching tool.” After all, the breaking ball breaks less at Coors Field.

This season no team is throwing their curveball lower than the Rockies. Consider the following chart:

Lowering Their Sights Season Rockies’ Avg. CB height at home plate MLB rank Avg. CB height at home plate in MLB 2015 1.76 ft. 19th 1.85 ft. 2016 1.83 ft. 21st 1.86 ft. 2017 1.63 ft. 30th 1.86 ft.

Consider this Chatwood curve location:

While the Rockies have thrown a relatively low percentage of curveballs (6.3%) as a club — as they have throughout the PITCHf/x era, only once reaching double-digits in usage — a healthy Bettis and Gray could change that. When Bettis returns, he — along with a healthy Gray — will give the Rockies five starting options of pitchers that throw curveballs at a 10% rate or better, along with Chatwood, Marquez (23.6%) and Jeff Hoffman (17.4%).

“I do remember having a talk about it. I think it’s something you hear a lot about,” Bettis said of avoiding the curveball at Coors. “I think it’s all about adjusting your sights and being comfortable in how you are throwing it.”

How difficult is it for a pitcher to adjust sights?

“Everyone is a little different, but for the most part everyone is pretty visual,” Bettis said. “If I wanted to throw a get-me-over strike, my sights would be on a right-handed batter’s shoulder and if it’s a left-handed hitter and I want to throw it for a strike or a back-door curveball, it’s going to start at an imaginary spot. So I have to be comfortable wherever that spot is — if it’s from Tony’s [Wolters] mask over to the right, or from the umpire’s mask over to the right — but it’s an imaginary spot. There is no target there. You have to work on all of that feel. [To lower sights] you have to lower that from shoulder to elbow or elbow to hip.”

Rockies rookie Kyle Freeland, a former first-round pick and Denver native, imagines a landing spot and a point at where the pitch should break.

While Black believed the curveball could work as Holmes’ did, Foster was a convert.

“The biggest thing I’ve recognized is the curveball works here,” Foster said. “I guess I was skeptical… not knowing how effective it would be, and I’ve been pleasantly surprised. It’s been a good pitch in Coors.”

The Rockies’ curveball has the lowest xwOBA (.178) in the sport this season, according to Baseball Savant.

While the slider has been the most effective pitch at Coors Field in the PITCHf/x era, Greg Holland’s slider has curveball-like action, dropping straight down off a seemingly invisible cliff. Statcast classifies the pitch as a knuckle-curve with an average height of 1.81 ft. at the plate. Holland is throwing it at a rate of 48% in what has been a come-back season.

The Rockies have brought back a focus to the curveball. They plan on throwing it more. They think they’ve figured out how to make the pitch play more effectively, and they believe it is the ideal secondary pitch to play off their preferred primary offering, the four-seam fastball.

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As the frequency of four-seam fastballs has declined throughout the game, the Rockies are going in the opposite direction: the Rockies have increased their usage of four-seam fastballs and currently lead the league in four-seams usage, 45.9%, up from 44.0% last season. The league-average usage rate for four-seam fastball rate is 35.6%.

“There’s intent,” said Foster of the four-seam/curveball combo. “You think about it, thin air, more spin. Physics. It makes sense. Four-seamers are harder than two-seamers, so we are talking about power and curveballs. You have variation of speed, and you have power; you have a faster fastball and a bigger variation. So those are things we talk about and discuss. Spin rate, four-seam fastball mixed with that curveball is critical. Those are things we see that are effective at Coors. It’s important.”

The Rockies are averaging 94 mph as a staff with their four-seam fastball, which is a team-best mark in the PITCHf/x era. The linear weight they have produced from fastballs is a record 13.1 runs above average, a club-record in the PITCHf/x era, and just the second time they have produced a positive linear weight.

The Rockies have raised the average height of their fastballs, too, but not significantly and perhaps that makes sense if a team wants to have a tunneling effect with the game’s lowest average curveball height.

Rockies’ average fastball height Season Avg. FB height at home plate MLB rank Avg. FB height at home plate in MLB 2015 2.49 ft. 26th 2.56 ft. 2016 2.48 ft. 28th 2.58 ft. 2017 2.55 ft. 21st 2.61 ft.

Perhaps it’s a mix of quality four-seamers and curveballs that can serve as a sustainable foundation of success for Colorado.

There’s no question that success off any mound begins with talent. Holland has proven to be an important offseason acquisition, Jake McGee has been dominant with better health and usage of data, and the Rockies are beginning to develop their own arms like Gray, Freeland, and Hoffman. But the Rockies also might be as close as ever to breaking the code, to finding a strategy, answers, at altitude.