Maybe the run-production environment (runs per game is currently at its lowest rate in 21 seasons) into which Harvey and Miller and their fellow precocious pitching peers have stepped is the root cause of the cluster, or maybe the cluster is helping cause the numbers.
Let's just set that aside as a chicken-or-egg-type discussion.
But there certainly seems to be a new generation of young guns ripening right before our eyes.
"There's enough tangible evidence to think so," Pirates manager Clint Hurdle said. "There could be a new wave of pitcher hitting the big leagues. We've seen Harvey and Miller, and they come as advertised. That Draft time has played out very well, very quickly."
It played out quickly for Hurdle's new No. 1 in training, Gerrit Cole, who debuted last week, almost two years to the day after he was taken first overall in the 2011 First-Year Player Draft. He has looked poised and polished through two starts, and if he can keep it up, perhaps by year's end he'll have opened as many eyes as Harvey and Miller and the like have.
In the meantime, there are five qualified starters aged 24 or younger who have ERAs of 2.50 or lower: the Mets' Harvey (2.04), the Cardinals' Miller (2.08), the D-backs' Patrick Corbin (2.28), the White Sox's Chris Sale (2.43) and the Nationals' Stephen Strasburg (2.50), who returned from the disabled list Sunday.
Just to put that in perspective, we haven't had a full season in which more than one starter aged 24 or younger posted an ERA of 2.50 or lower since 1987, when the Cards' Joe Magrane (2.18) and the Twins' Allan Anderson (2.45) pulled it off. And you have to go all the way back to 1972, when the Reds' Gary Nolan (1.99), the Mets' Jon Matlack (2.32) and the Yankees' Steve Kline (2.40) each had a sterling season, to find the last time we had more than a pair.
Maybe the second half of the season will fluctuate those ERAs out of that particular statistical picture, but something interesting seems to be brewing.
"It doesn't happen a whole lot in the game," Reds veteran Bronson Arroyo said. "Usually, when you compare the Major League level vs. Triple-A, it takes a while to find that comfort level and understand that the organization doesn't view you as a guy who deserves to call his own game yet and the qualities that come with that. It took me at least four years to get to that point."
Harvey and Miller didn't need four years, or even four months. Granted, we must be careful not to get too far ahead of ourselves, because the process of becoming a true ace can't be rushed, but Harvey and Miller have already elevated themselves to the level of must-see TV, if nothing else, and people around the Major Leagues certainly have taken notice.
"Finding guys like that is a needle-in-the-haystack type of thing," Giants veteran reliever Jeremy Affeldt said. "Even if you throw hard, you still have to have the confidence and the boldness to throw to big league hitters with command. That's what's impressive with those guys. I think Harvey might be ahead of Miller with fastball command and mixing it up, but Miller's got a really good fastball. It's explosive."
Average fastball velocity among starters has risen a full tick, from 91.4 to 92.4 mph, just in the last five years alone, according to FanGraphs.com, and the young guns have done their part to contribute to that. Cole's fastball has averaged 96 mph in his two starts, the highest such average among starters in the game. Strasburg (95.5), 22-year-old but since-optioned Orioles right-hander Kevin Gausman (95.3), 24-year-old Rays righty Chris Archer (95.2) and Harvey (95) have also averaged 95 or higher.
But as Gausman's demotion a few days ago illustrates, velocity alone can't help a pitcher survive at this level. Poise counts. And when you consider that four of the 21 starters who entered this week with a WAR of 2.0 or higher were in the 24-and-under crowd (Harvey, Miller, Sale and Corbin), the conclusion is that poise does not necessarily require experience.
"I don't know if this group is the first version of guys that have played baseball and baseball only since they were eight -- the traveling group generation -- or what it is," said Reds pitching coach Bryan Price. "Maybe it's just the advances in scouting and finding the right guys."
Whatever it is, it's an exciting time for fans of the well-pitched ballgame. The current environment is such that a prized prospect like Zack Wheeler comes along to make his debut start for the Mets tonight, and it feels as though he has an abnormally difficult standard to live up to.
"In the early 2000s," Affeldt said, "you had Josh Beckett and Zack Greinke and A.J. Burnett and John Lackey. It's kind of like that time period, where you see young aces come up at once. They're hard throwers, and these guys have the command with the hard-throwing [ability]. That's what makes a good starter, when you have the velocity to go with the command."