You know how this works: Early into any season, many of us get obsessed with checking on fastball velocities. Big positive changes might portend great success — or surgery. And big negative changes might indicate future struggles — or surgery. It’s all guesswork in the first half of April, but it’s something, something potentially meaningful. Fastball speeds generally don’t lie to you. It’s this line of thinking that brought Jake Arrieta to my attention a short while ago; out of the gate in 2017, Arrieta wasn’t throwing the same stuff. He’s a high-profile pitcher, who’s put up high-profile numbers, and so any change is an important one.

I’ve kept my eye on Arrieta. I tend to dismiss pitchers who are dismissive of velocity changes, because they all say the same thing. At the end of the day, velocity loss is correlated to performance decline. There are exceptions, but there are exceptions to almost everything. Yet, there’s a complicating factor here. Arrieta’s velocity is down, and on its own, that’s troubling to me. But within context, perhaps we’re just observing something intentional. You know who else has lost velocity? Jon Lester. Also Kyle Hendricks. Also John Lackey. And also Brett Anderson. All the other guys in Arrieta’s starting rotation.

For this look, I made use of the Baseball Prospectus PITCHf/x leaderboards, powered by Brooks Baseball. I combined four-seamers and sinkers to find overall average fastball speeds. I found 130 starting pitchers who’ve thrown at least 50 fastballs in both 2016 and 2017. Here’s a plot of their year-to-year average velocities, with the five Cubs starters highlighted in blue.

The average starter so far has lost 0.5 miles per hour. That’s to be expected; it’s April, and pitchers are still building up their arm strength. But Anderson is down 1.5 ticks. Lester, 1.7. Lackey, 2.3. Arrieta, 2.7. Hendricks, 2.8. To put it another way: Hendricks owns the second-biggest velocity dip. Arrieta’s tied for third, and Lackey is sixth. Lester is tied for 16th, and Anderson is tied for 20th. All five pitchers are easily in the bottom 20%, and that’s a tough thing not to notice. Any individual case makes you wonder or worry about an injury. When you have a team-wide pattern, you consider other explanations.

One thing I should note to go along with this: Cubs starters are 10th in baseball in ERA-, and 7th in FIP-. Last year, they were 1st and 3rd, respectively. They’ve performed a little bit worse, but they’ve still been plenty good. And nobody around the Cubs seems to be the least bit worried.

Heck, I’ll just keep on going. One way to examine things is by looking at average velocity. Another way is by looking at peak velocity, which Brooks Baseball tracks. Relative to last year’s best fastball, Anderson and Lester are both down 2.8 ticks. Hendricks is down 3.1, Arrieta is down 3.7, and Lackey is down 4.3. There are many more bullets to be fired, but none of these guys has gotten real close to last year’s top speed. It’s just further evidence of what we were already looking at. The fastballs aren’t the same. Not through the earliest couple of weeks.

How might this be explained? There could conceivably be some lousy calibration. Maybe the pitches just haven’t been measured right. I’m skeptical, since it’s seemed like opposing pitchers have been basically normal, but there’s a chance. There’s also a chance that, hey, all five pitchers are having simultaneous issues getting right! It’s crazy to think about, but seldom does a pitcher *want* to lose zip. I remain skeptical, because that’s five pitchers at one time. That’s too many pitchers, even by 2017 Dodgers standards.

The potential explanation I find the most interesting: This could be something the Cubs are doing on purpose. Two years ago, the Cubs advanced to the NLCS. Last year, the Cubs won the World Series. This year, the Cubs are expected to make another deep run, and they ought to take the NL Central without too much of a fight. Not that a team should ever take anything for granted, but just based on the rosters and the math, these Cubs ought to play more than 162 games. We’re looking at longer seasons, and shorter offseasons. More time spent pitching, and less time spent recovering. Wouldn’t it make sense to open the season by having your starting pitchers try to back a little off?

On my part, this is entirely speculation. I don’t have any Cubs-specific insight. I also don’t know how easy it is for a pitcher to try to throw his fastballs at 95% instead of 100%. That might mess a guy up, for all I know. But maybe, just maybe, the Cubs are intentionally trying to ease their starters in, so that they might have more energy left come September and October. That’s not something I can recall ever seeing, but I see how it might be a workable theory. With all due respect to the Cubs’ divisional rivals, finishing first shouldn’t be too hard. Especially with the Cardinals slumping, and with the Pirates losing Starling Marte. The Cubs won’t finish in first by default, but they can probably afford to take things a little easier, at least from the get-go. So, hey, it’s a guess. Maybe it’s accurate. Which would be very cool, and a little bit cocky.

It’s easy to spin any velocity loss into a bad thing. In the Cubs’ case, it’s not too hard to spin this collective loss into a good thing, of sorts. I don’t know if my theory is right, and I don’t know if there are physical issues at the moment. But looking at the context, I feel better about Arrieta now than I did when I thought he was all by himself. There’s a certain amount of safety in numbers.