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There was a range of opinions on the St. Louis Cardinals’ acquisition of Jason Heyward last Monday, but the most common one was: The return the Braves got for Heyward, an elite right fielder, sure wasn’t sexy. They had to toss in a solid right-handed reliever, in Jordan Walden, just to get Shelby Miller—a struggling young pitcher whose future is uncertain—and Tyrell Jenkins, a high-ceiling but frustrating pitching prospect yet to see Double-A. It wasn’t necessarily a mistake, if one assumes that Atlanta knows what it’s getting in Miller and thinks he can regain his 2013 form, but it sure seemed underwhelming.

It seems to me, though, that Jenkins is the real key to the deal. He’s the one who can tip things in the Braves’ favor. A 2010 sandwich-round draft pick, Jenkins is the sort of player old scouts drool over, but they drool into their spit-cups, not down their shirtfront. He inspires imagination, but his flaws are real and ever in evidence. He throws a very good, live fastball, and could eventually have two secondary pitches—a curve and a changeup—that work at an above-average level in the Major Leagues. He could also fail to ever get there. He’s battled shoulder injuries, an inability to find a consistent arm slot and the difficult development of those secondary pitches throughout his professional career, and had ugly numbers even this season in the Florida State League.

However, Jenkins impressed relentlessly in the Arizona Fall League this autumn, and the Braves are just the kind of team that would trust their scouts’ assessment of when a prospect has turned a corner. They seem to have targeted Jenkins because they genuinely believe that his newfound success is real, and will last. That seems a reasonable position, given the promise into which Jenkins always seemed so close to tapping.

But then, you ask, why would the Cardinals let Jenkins go? The answer here is pure logistics. Jenkins, having played in five professional seasons, was due to be added to the 40-man roster by Nov. 20, or else be exposed to the Rule 5 Draft. The Cardinals aren’t in position to add a player like Jenkins right now. This is a common symptom of success, in the modern game. Teams with both strong big-league rosters and deep farm systems occasionally leak talent, losing a player any team would like to retain because they simply can’t fit all of the good players they have into the roster spots available.

St. Louis did very, very well to leverage Jenkins’s breakout month or two, trading him at a high point in value even as a deadline loomed that affected only their side of the trade. The Braves, who are moving toward a rebuilding phase and are thin in terms of upper-minors talent, had plenty of room to add Jenkins to their 40-man reserve list. Coase Theorem rarely works in baseball; there are too many externalities in play to make the market truly efficient. This time, to the credit of both sides, the Braves and Cardinals found a perfect fit.