Miami Marlins' Giancarlo Stanton (27) rounds the bases after hitting a two-run home run off Atlanta Braves starting pitcher Alex Wood, right, during the third inning of a baseball game, Tuesday, April 29, 2014, in Miami. (AP Photo) Alex Wood after Giancarlo Stanton's home run. (AP photo)

Credit: Mark Bradley

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Credit: Mark Bradley

Well, we knew it wouldn't last forever. Over the season's first 21 games, no Atlanta Braves starter yielded more than three earned runs in a game and only one had yielded even three. In Game No. 22, Ervin Santana was touched for four. (Banish him to the bullpen!) In Game No. 25, Alex Wood surrendered seven. (Send him to Gwinnett!) And now the rotation, which posted an ERA of 1.50 through 21 games, has seen that number rise to 1.90. Which is still, we emphasize, the best in the majors by half a run a game.

David Schoenfield of ESPN's SweetSpot noted Monday that, over the past 30 years, only six rotations have posted an ERA lower than 2.00 in a calendar month :  The Phillies in June 2011 at 1.96; the Cubs in April 1985 at 1.94; the Braves in July 1992 at 1.92; the Nationals in April 2011 at 1.78; the Cubs in July 1992 at 1.72 and the Braves in August 1994 at 1.61. (And here we note that August 1994 was skewed because it contained only 10 games, the baseball season being truncated by the players' strike.)

The 2014 Braves are still positioned to join that list, provided Aaron Harang doesn't go and give up a grand slam or two tonight in Miami.(UPDATE: Sure enough, Harang yielded nine earned runs Wednesday, which pushed the ERA of the Braves' rotation to 2.32 for the entirety of April. Bummer.)

Speaking of Harang, here was another numerical nugget from Baseball Reference last week:

Baseball Reference also notes that only seven other pitchers over the past 100 years had opened a season with five or more starts of at least six innings and no more than one earned run. The longest such streak belonged to Fernando Valenzuela with seven such starts to begin the 1981 seasons. (For an in-depth look at Harang's hot month , there's this from the always excellent Ben Lindbergh of Baseball Prospectus.)

If we're asking, "Can these guys keep it up?", the answer is -- and was even before the 16 earned runs surrendered on two Miami nights -- a resounding no. The 2014 Braves can continue to pitch well, but there's no way they'll pitch this well for much longer. Of Harang, Michael Beller of SI.com writes:

He has a .200 BABIP and 89.3-percent strand rate, two numbers that simply cannot last. Additionally, he has always been a fly-ball pitcher, and that hasn't changed this year, evidenced by his 52.9-percent fly-ball rate. However, he has yet to allow a home run this year. While there are certainly worse places for a fly-ball pitcher than Turner Field to call home, some of these fly balls are going to start sailing over the fences soon.

BABIP stands for batting average on balls in play, and that's a favorite measure of sabermetricians in search of "sustainability." A BABIP that's unusually low for a pitcher -- or unusually high for a hitter -- suggests that a regression to the mean is coming soon. Strand rate refers to how many baserunners score, which numbers-cruncher believe is also a function of luck. Writing Monday, Schoenfield of ESPN addressed that very concept :

How much of the Braves' success has been luck? Their starters do lead the majors in home run-to-fly ball ratio, allowing home runs on just 5 percent of the fly balls they've served up (pitchers tend to gravitate around 10 percent). They're also second to the Reds in strand rate, at 84.7 percent. That's how you post a sub-2.00 ERA. That doesn't mean the Braves' rotation has been completely lucky -- it does lead the majors in swing-and-miss percentage at 26.1 -- but that home run rate and strand rate are what we'd call unsustainable.

We know already that the rotation that propelled the Braves to first place in the season's first month is subject to change. Mike Minor is scheduled to make his 2014 debut on Friday, and Hale, who just worked eight innings and yielded two hits and one earned run against the Reds, will be bumped to the bullpen . And then there's Gavin Floyd, who was signed over the winter as rotational insurance. What do the Braves do with him?

The good thing about having too many pitchers is that, in baseball, you can never have too many pitchers. Something always happens. Arms get sore. A hot first month can devolve into a chilly summer. As great as the Braves' starting pitching has been to date, the season isn't even one-sixth done.

From myajc.com, our premium site: The Braves' pitching? Still great, somehow.

From last week: The Braves' rotation has been nothing but quality.

From two weeks ago: Aaron Harang - no no-hitter, but what an April!