Maybe we should have seen this coming. It was pretty clear that the Braves were going to trade an outfielder this winter, with both Justin Upton and Jason Heyward entering their final season before they became free agents, and the team apparently preferring to employ Evan Gattis as a left fielder rather than as a catcher. The team tried to re-sign Heyward when they spent last year locking up their young core, but found his price prohibitive, so he almost certainly wasn’t staying in Atlanta beyond the 2015 season, and the Braves probably aren’t good enough to be pushing all of their chips in for the upcoming season.

So, trading Heyward now makes a good amount of sense for the Braves, and they made it clear that acquiring starting pitching was their #1 priority this winter. A natural trade partner would have a hole in right field, some rotation depth, and the potential desire and ability to try and sign Heyward to a long-term deal before hit the open market next winter. No team in baseball fit that description as well as the St. Louis Cardinals, so while we didn’t hear any pre-deal rumors of the deal that sent Shelby Miller and Tyrell Jenkins to Atlanta for Heyward and Jordan Walden, it feels like we should have anticipated something like this. It’s the kind of move that seemingly makes a lot of sense for both sides.

We’ll start with the Cardinals side of things, since they’re acquiring the best player in this deal. Jason Heyward is a stud, and you don’t even have to buy into defensive metrics to agree with that statement. For 2015, Steamer projects him at +4.5 WAR per 600 plate appearances, the 16th highest total of any position player in baseball, and that’s with him grading out as just a slightly above average defender: the +10 fielding projection right field adds up to a +3.5 DEF rating, which includes the positional adjustment for playing a corner spot. In terms of forecast defensive value, Heyward’s projection puts him in roughly a similar group to guys like David Wright, Robinson Cano, Pablo Sandoval, and Josh Reddick.

It’s also a significant step back from what he’s done previously, as his career DEF/600 PA rating is +10. In other words, Steamer is projecting Heyward to take a big step back defensively and still be one of the best players in the game, because the forecast sees a 25 year old with a career 117 wRC+ and positive contact rate trends, so it thinks Heyward is on the verge of a big offensive breakout. From a purely offensive standpoint, Steamer expects Heyward to be as good (or slightly better than) the good Upton, Matt Kemp, Ryan Braun, or Hanley Ramirez. If you combine the offensive level of those players with above average defensive value, well, you’re left with a superstar.

And that’s why the Cardinals have to be pretty thrilled with this move. They’re legitimately getting one of the best young players in baseball, and at the only position where they had a glaring need. Adding Heyward to fill their right field hole will end up being one of the largest improvements any team makes this winter. The question for the Cardinals is how long they’ll get to keep him.

Because of how quickly he got to the big leagues, Heyward is in line to hit free agency after his age-25 season, and he’s going to have roughly +25 career WAR when he reaches the open market. Barring a disastrous 2015 season, he’s going to get paid, and you can be certain that his agents will be pointing to the 13 year, $325 million deal that Giancarlo Stanton has agreed to as the new precedent. Sure, Heyward isn’t going to get 13/$325M, given the massive differences in power, but it seems likely that he’ll demand a deal that starts at 10 years and goes north of $200 million.

Robinson Cano got $240 million as a similarly valuable player entering his age-31 season; Heyward might not have Cano’s offensive track record, but he’s going to be selling his prime years, and the deal won’t extend into the period of his career where you’d expect him to essentially be worthless. If the Cardinals want to lock up Heyward before he gets to free agency, it’s probably going to take something like the contract they refused to give Albert Pujols. Maybe they might be able get him to take a slight pre-free agent discount and get him for 9/$200M or something in that range, but let’s dispel the notion that the Cardinals are going to be able to sign Heyward for anything other than a mountain of cash.

The team definitely has the means to take on a contract like that. They only have $73 million in committed contracts for next season, and Matt Holliday’s contract expires at the end of the 2016 season, so they have the flexibility to make Heyward a franchise-player type offer. And they do have a history of acquiring players on the cusp of free agency, only to convince them to stick around instead, but stretching for a single player the way Heyward will require would be something new for this front office.

For now, this has to be viewed as a rental. A rental with a chance to purchase, perhaps, but this isn’t a trade-and-sign deal like we’ve seen with the R.A. Dickey or Martin Prado trades the last few years. The Cardinals are getting a great right fielder, but they’re only guaranteed to get him for one year, and then it’s either a really large long-term commitment or settling for the compensation pick that comes from letting a premium free agent walk away at year’s end. There’s a non-zero chance that the long-term return on this deal for St. Louis will be minimal.

But the short-term upgrade is huge, especially if they flip Peter Bourjos for a starting pitcher to replace Miller, which shouldn’t be too terribly difficult. Having Heyward/Walden/Pitcher To Be Named instead of Bourjos/Miller/Jenkins could be a three or four win upgrade in 2015, depending on what kind of starter they get in return, and that’s three or four wins in a year in which marginal upgrades are going to be extremely valuable to the Cardinals.

Adam Wainwright is probably just about finished as an ace, and is headed for a decline. Yadier Molina won’t be able to hit forever. Holliday isn’t a spring chicken anymore. The Cardinals have plenty of good young talent, but their best players are getting worse, and the Cardinals needed a significant upgrade to put themselves in position to win the NL Central once again. This move does just that.

The long-term cost will essentially boil down to what you believe Shelby Miller is. Is he a top-flight young pitcher, the guy who has produced +6 WAR by runs allowed in 370 big league innings, and just turned 24? or is he a two-pitch tease, overrated by run prevention, heading for a short-term crash when his mediocre peripherals catch up with him? A strong case could be made for both outcomes.

Miller throws a lot of fastballs up in the zone, and as Eno noted through multiple conversations with pitchers this year, high fastballs can produce some terrific results, often inducing a lot of useless contact that isn’t captured in FIP-type metrics. If Miller’s approach to pitching up with a good fastball makes him a guy who can sustain a BABIP in the .270-.280 range, the underwhelming strikeout rates become a lot less problematic. If you’re a Braves fan who wants to be excited about this deal, here’s the first ~400 IP comparison you want to use.

Name IP BB% K% GB% HR/FB LOB% BABIP ERA- FIP- xFIP- Shelby Miller 370 9% 20% 39% 10% 79% 0.267 92 110 110 Matt Cain 437 10% 20% 37% 6% 72% 0.259 83 86 102

Cain was always better at home run prevention than Miller, but the template is similar, and it’s certainly possible that Miller is a (somewhat worse) new version of the Cain skillset. If Miller’s FIP-beating ways prove sustainable to a significant degree, picking up four discounted years of a quality young arm is a very solid return for a single year of Heyward, especially if the Braves don’t see themselves as strong contenders in 2015.

But Cain is notable because most pitchers can’t do what he’s done, and not every young hurler who posts a low BABIP for 400 innings is definitely going to follow in his footsteps. Here’s another, less-rosy comparison for Miller, again with career performance through the equivalent of two full seasons.

Name IP BB% K% GB% HR/FB LOB% BABIP ERA- FIP- xFIP- Jeremy Hellickson 402 8% 17% 38% 10% 82% 0.244 79 115 110 Shelby Miller 370 9% 20% 39% 10% 79% 0.267 92 110 110

A couple of years ago, the arguments for Hellickson were the same as they are for Miller today. Maybe he’s just good at inducing a lot of popups, and because he’s a flyball guy, he’s always going to run lower than average BABIPs, so he’s underrated by metrics that focus only on walks, strikeouts, and home runs or ground balls. Hellickson managed to keep things going through age-25, and then promptly fell apart, pitching poorly and getting injured. The Rays just shipped him to Arizona for two lower level prospects rather than bet on him returning to prior form.

More often than not, guys who post big gaps between their ERAs and their FIPs regress towards the latter, which is why FIP and xFIP work for most pitchers. It doesn’t mean Miller is definitely not an outlier, but he probably isn’t at outlier to the degree that he’s been so far, and he’s probably more of an okay pitcher than a very good one.

But even four years of an okay young arm is pretty valuable. After all, we’re looking at league average starters making $10-$12 million per year in free agency, and Miller will a little more than the league minimum this year, with three below-market arbitration years to follow. Even if Miller is more of a solid arm than a future ace, the Braves are getting a lot more quantity of value here, and they’re allocating it into the years where they think they might be more able to contend.

And Miller isn’t the only thing they’re getting. Tyrell Jenkins was a first round pick a couple of years ago, and while he’s battled arm problems since, Kiley McDaniel remains somewhat intrigued by his potential. Here’s Kiley’s updated take on Jenkins:

Jenkins missed the first half of 2014 recovering from shoulder surgery on a muscle in his shoulder (not the joint itself), something that had been bothering him for years. He turned 22 in the middle of this season and was understandably a bit rusty in half a season at High-A, but started to find his stride in the Arizona Fall League, where I scouted him a few weeks ago. He sat 92-94 and hit 96 mph, flashing above average fastball life at times, with an above average 80-83 mph hard curveball and a changeup at 81-84 mph that’s average when he keeps it down in the zone. He’s incredibly athletic and the breaking ball has flashed plus at higher velocites, so there could still be even more in the tank than what I saw. I’d like to get a full, healthy 2015 on the books for Jenkins before i give a projection with some certainty, but he seems to be headed in the right direction now with enough starter traits to project him in a rotation. I’d grade him as a 50 FV/#4 starter now, but I could edit that up a notch by the middle of next season.

The combination of Miller and Jenkins give the Braves two live-arms that they’re buying somewhat low on, and if both end up pitching to their previously-believed potential, this would turn into a huge win for Atlanta. If either of them turn into quality mid-rotation starters, or if you think Miller is already that now, then this probably is a smart enough move for a somewhat-rebuilding team to divest a short-term asset into some future value.

Of course, if Miller is Hellickson 2.0 instead of Cain 2.0, and Jenkins is just another power arm who can’t miss bats, then this could look pretty terrible for the Braves as well. If Steamer is correct about Hewyard’s impending breakout, this could turn out to be a franchise player for a couple of arms with legitimate question marks who might turn out to be nothing at all. This move could be great, okay, or terrible for Atlanta, and it all depends on how the young arms develop, which is maybe the most difficult thing to project.

The fact that there’s no obvious most likely outcome suggests this is a pretty fair move for both sides. I probably prefer this a little bit from St. Louis’ perspective, since I lean more towards assuming Miller’s strikeout regression is a concern, but even I’d still say this is a fair return for a single year of a player looking at a monster paycheck next winter. The Cardinals get better now, and get a chance to make Heyward the new face of their franchise, while the Braves probaby get better for the future.

And that makes this seem like a smart trade for both teams. The Cardinals get the better player and a chance to extend a player the Braves weren’t going to keep, while the Braves get some good young pitching to make a stronger run in 2016. This is a deal that serves the purposes of both sides. It might end up favoring one or the other, but at the time of the deal, it makes sense for both Atlanta and St. Louis.