The best rotation in baseball so far this season was an accident. Years of scouting and strong drafting left the Braves with an almost unparalleled trove of young talent as the decade turned to the 2010s, along with a plan to surge through their cost-controlled near-peak years. Aaron Harang (0.85 ERA) wasn't part of the plan four years ago. Ervin Santana (slacking a little bit with a 0.86 ERA) wasn't part of the plan two months ago.

But the best rotation in baseball was the story of a little luck and a fast response to a sudden crumble.

The worst rotation in baseball to date, and the one that could cost some very longtime baseball persons their jobs, started with a plan too. This Arizona plan wasn’t the Braves dreaming on their untouchable four of Julio Teheran, Mike Minor, Randall Delgado and Arodys Vizcaino (the last two of whom became touchable). This was real. This was in the major leagues two years ago.

It was a young rotation with spare parts, and overall, it was a pretty good staff. Their ERA doesn’t look great in that ballpark, but the staff put together a 104 ERA+, better than average after adjusting for ballpark. And these were the pieces in place:

Joe Saunders, 31
Ian Kennedy, 27
Josh Collmenter, 26
Daniel Hudson, 25
Wade Miley, 25
Trevor Cahill, 24
Patrick Corbin, 22
Trevor Bauer, 21
Tyler Skaggs, 20

Strip away everything you know now—the 7.15 rotation ERA dragging down a 5.58 staff ERA dragging down a 6-18 ballclub that has gotten so embarrassing that it went undercover as the Kansas City Packers and finally won one on Wednesday.

Strip that all out of your memory. The 2012 season comes to an end. Which direction do you see that rotation heading?

OK, how about when you’re told that the next offseason they added (in transactions that didn’t involve any of the above):

Brandon McCarthy, 29
Randall Delgado, 23

In hindsight, the fact that they went out and got those guys may have been the first indication that something was starting to go wrong. Saunders was a free agent who was never counted on to be part of the team. Bauer, a once-elite prospect whose luster had faded, was traded to the Indians. But there was still a surplus going into 2013. Kennedy, Miley, McCarthy, Cahill and Corbin were named to the Opening Day rotation. Collmenter to the bullpen. Hudson to the DL. Delgado and Skaggs quite the pairing headed to Triple-A.

It wasn’t an All-Star team, but it was a legitimate rotation with very legitimate depth, an important consideration given that sixth and seventh starters always find a role in season.

But there was an underlying problem. What there was in the major leagues was just about all there was in the organization. Here are the top 10 prospects in the organization at the outset of the 2013 season per Jason Parks’ list.

1. LHP Tyler Skaggs
2. RHP Archie Bradley
3. SS Chris Owings
4. 3B Matt Davidson
5. SS Didi Gregorius
6. C Stryker Trahan
7. LHP Andrew Chafin
8. OF Adam Eaton
9. C Michael Perez
10. OF A.J. Pollock

Seven position players, three pitchers. Of the three pitchers, one was already counted, one is still being kept down in Triple-A, and another who is currently repeating Double-A and has fallen off the list.

If this rotation held up, it was probably going to be OK. But if it didn’t, the depth just wasn’t there anymore. And when the injuries started, it all fell apart.

Kennedy was traded midseason. Corbin needed Tommy John surgery. Skaggs was traded back to the Angels in order to fill a power void, and that’s where this whole mess of an organization starts to become one continuing narrative. On the surface, the fact that they traded away Justin Upton, which still hangs over pretty much every conversation about this organization, isn’t why they’re losing. They have a -60 run differential, and these offensive numbers aren’t good, but even when you consider a good offensive ballpark, they aren’t -2.5 runs per game bad.

When you’re trading from a deceptively thin rotation to fill a power void, though, it all starts coming together. Certainly the players themselves can’t be excused here. Even with all that’s gone on with the roster, each of the four primary starters thus far is performing worse than his PECOTA projection, and in some cases far worse than even the 10th-percentile forecast.

Bronson Arroyo
9.50 ERA (10th percentile: 5.06)

Brandon McCarthy
6.23 ERA (10th percentile: 4.65)

Wade Miley
4.50 ERA (40th percentile: 4.54)

Trevor Cahill
7.48 ERA (10th percentile: 4.96)

(Note: This was a much less pleasant exercise than doing this with the whole roster of the 2013 Red Sox to see how they outperformed their expectation by so much.)

There is some bad luck here, too. If you want a Reds exile on your team, which one do you want, Arroyo or Harang? That’s just YCPB. But no matter how good things looked for Arizona at the major league level and how good the team’s top prospect in A ball was, this shows just what can happen with a gap in the pipeline if you don’t act quickly and get lucky like the Braves.

Arizona is starting to act, however slowly. Cahill and Delgado have already been booted from the rotation, and we’ll probably see Bradley sometime soon—whether now-ish, with the seventh year of control guaranteed, or after the Super Two cutoff in June.

Bradley’s arrival will patch things up, but it won’t change how fast you can go from promising to extremely problematic.