The Rockies were this offseason’s popular dark horse. Not everybody agreed on that, naturally, but if they did, then the Rockies wouldn’t have been a very good dark-horse candidate. A team has to be rated low in order to be underrated, and there was plenty of chatter the Rockies could surprise and push for the wild card. The FanGraphs community determined the preseason projections were too low on the club, so coming in, there was a certain amount of hype. There was faith! Faith in the Colorado Rockies.

Among the things that have happened: Ian Desmond got hurt. Tom Murphy got hurt. Tony Wolters got hurt. Jon Gray got hurt. David Dahl got hurt. And Chad Bettis got sick. Over the course of the last few months, the Rockies roster has been beaten and battered. And it’s also managed to win 22 of 35 games. At this writing, it’s the Rockies who are on top of the NL West, and it’s the Rockies who have so substantially boosted their own chances of making the playoffs. For the first time in so many years, the Rockies could be delivering on their promise. There are two major reasons why they are where they are.

Interestingly enough, this doesn’t have a lot to do with the hitters. There have been some bright spots, like the suddenly fascinating Mark Reynolds, but the Rockies rank just 13th in runs per game, and that’s without adjusting for ballpark. By wRC+, the Rockies are a woeful 27th, and although I’m open to the idea that wRC+ is unfair to the Rockies’ bats, they still haven’t been good, not overall. The story of the season to date is all about run prevention.

On that side of things, the Rockies rank 14th in runs allowed per game. Taking ballpark into account, the Rockies shoot all the way up to second in baseball in ERA-. This is a staff that hasn’t had Gray or Bettis. It’s a staff that intended to lean on Gray and Bettis. The reinforcements and the existing support system have done the job, and as a critical component of this, there are the grounders. The Rockies have been giving up grounders.

Here’s how the Rockies’ pitching-staff grounder rate has progressed year to year:

The team has reached a new high within the observed window, and this is the highest team grounder rate in the game. Obviously, when you’re talking about Coors Field, there’s reason to believe it’s better for a pitching staff to keep the ball on the ground. Anything in the air is dangerous. Some credit goes to Kyle Freeland. Also guys like Tyler Chatwood and Chris Rusin. Plenty of grounders have been there, which makes the next plot all the more encouraging. You might not recognize sOPS+ as a statistic. That’s something tracked at Baseball-Reference, and it’s essentially OPS+ within a given split. Let’s look at opponent production against the Rockies on grounders:

An sOPS+ of 100 is league average. Last year, when the Rockies got grounders, they allowed an sOPS+ of 107. That means they were something like 7% worse than average. This year, so far, that number has dropped to 71, meaning they’ve been something like 29% better than average. To put this much more simply: The Rockies have generated more grounders, and they’ve been much better at turning those grounders into outs.

That’s a fun thing to explore. I’ll borrow some information from Baseball Savant. Here’s where the Rockies have ranked in average ground-ball exit velocity:

2015: 19th

19th 2016: 14th

14th 2017: 2nd

To support that, from a different source, here’s where the Rockies have ranked in ground-ball hard-hit rate:

2015: 23rd

23rd 2016: 20th

20th 2017: 2nd

Based on the evidence we have, the grounders have been more weakly hit. I don’t know how to explain that, necessarily, but that doesn’t mean it’s wrong or impossible to keep up. For now, it’s just a thing. And there’s this other interesting data point, regarding the defense. Better performance on grounders would probably involve the pitchers and the defenders, right? Last season, the Rockies ranked 8th in defensive shifts. This season, they rank 27th. They’re having fewer alignments being classified as shifted, and while that might seem counterintuitive, last year the Cubs had fewer alignments classified as a shift than anyone. It doesn’t mean defenders aren’t still being used well. The Rockies have had many of the same players, but they’ve done better, and they’ve been positioned differently. So far, the synergy of it all has been through the roof.

That’s one thing. One major reason why the Rockies are in first place is because they’ve gotten grounders and swallowed them up. Then there’s the matter of the bullpen. The bullpen is the other major reason. I like to look at how bullpens fare through the lens of Win Probability Added. Let’s examine some year-to-year Rockies ranks, shall we?

To make sure you’re reading that correctly: Last year, the Rockies bullpen had baseball’s worst WPA. It was the least valuable bullpen in the game. So far this year, the Rockies bullpen has baseball’s best WPA. It’s been the most valuable bullpen in the game, and it’s not even all that close. Because it’s only May 11, it’s not like we can reach any firm conclusions, but in case you’re curious, we’ve got WPA data stretching all the way back to 1974. Only one team’s bullpen has ever gone from worst to first, and that was the 2008 Rays. That Rays team ultimately advanced to the World Series. The Rockies would have a very limited precedent, and a very promising one.

The Rockies bullpen always looked intriguing. It was going to hinge on getting healthy versions of Greg Holland, Jake McGee, and Adam Ottavino. So far, so good, mostly. And the front office also threw Mike Dunn into the mix. Those four relievers are the four relievers on the team who’ve entered with average leverage indices of 1 or higher. I decided to do a league-wide browse, looking at how all the teams have performed when narrowing down to only the relievers meeting the same criteria. These are the relievers teams have trusted the most. We know the Rockies rank first in WPA to date. Just looking at the higher-leverage guys, the Rockies relievers are 4th in ERA- and 4th in FIP-. They’re also just 12th in xFIP-, so a few homers could make things worse, but you can’t assume homers until they happen. The group looks pretty good, and it’s already been great.

Performance through five weeks has only a limited relationship to performance the rest of the way. Nothing for the Rockies is going to come easy, and they’re going to need to hit a little more than they have. They’re probably going to allow more home runs, and the bullpen is going to mix in the occasional clunker. But you can see why things are looking up. The relievers have delivered on their preseason promise. And despite the adversity with the state of the starting rotation, the pitchers the Rockies have had have churned out a bunch of grounders, and the defense has been good about handling them. This is a Rockies team you have to take more seriously than others from the past few seasons. They might not be all the way there yet. There’s plenty of room for improvement. But considering the storm they’ve had to weather, things couldn’t have gone much better than they have.