The St. Louis Cardinals announced today that they have traded pitchers Shelby Miller and Tyrell Jenkins to the Atlanta Braves in exchange for outfielder Jason Heyward and pitcher Jordan Walden.

The big names here are obviously Heyward and Miller, and nobody's going to argue that the Cardinals aren't getting a hell of a deal. Heyward, still just 25 years old, is fresh off a season in which he reclaimed a bit of his power stroke—his 21 homers were the most he's hit since clubbing 27 in 2012—yet again proved himself to be one of the best defensive outfielders we've seen in a long time. Check out where his career value ranks among all outfielders through their age-24 season over at Baseball Reference, by the way; he's actually been quite a bit better than $325 million man Giancarlo Stanton, who's the same age and has had basically the same playing time.

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Miller, on the other hand, hasn't shown much to get excited about during his first two full seasons as a starter. Miller was once one of the best young arms in the Cardinals' system, but last year his walk rate ballooned while his strikeout rate dropped, and his 3.74 ERA was a much better mark than he deserved. (His FIP was 4.54, in part due to an utterly unsustainable BABIP of just .256.) At just 24 years old, Miller still has time to reach his potential, but the Braves have just traded a very good player for a ... not very good player. What gives?

The Braves were probably going to lose Heyward in the offseason anyway, and now they've got four years to get Miller right and six years to hope that Jenkins—the 17th rated prospect in the Cards' farm system as of 2013—turns into an actual player. I guess this works if you're an actuary, but have fun watching Shelby Miller try not to walk six guys every start instead of one of the most exciting outfielders in the game, Braves fans.