Ten days from the trade deadline, we usually spend most of our time talking about whatever star player is eligible for free agency at years end, and is on a non-contending team looking to upgrade for the future. David Price, Johnny Cueto, and Yoenis Cespedes last year, for instance. This year, though, that guy doesn’t exist; the big pending free agents on rebuilding teams are guys like Rich Hill and Jay Bruce. And because of the dearth of quality players likely to change teams over the next week and a half, the guy who is generating the most conversation leading up to the deadline is… Kyle Schwarber?

Yes, at this point, the hot name that everyone wants to talk about is an injured 23-year-old catcher/outfielder who won’t be healthy enough to play again until next year. Despite the Cubs best efforts to tamp down rumors, leaks out of New York keep suggesting that Schwarber is the guy the Yankees covet, and given the Cubs well-known interest in Andrew Miller, there appears to be mutual interest in players from both sides, with a stand-off emerging over whether the Cubs should surrender Schwarber in a deal for the game’s best left-handed reliever.

The Cubs continue to insist they aren’t going to do it, seeing the move as shortsighted, giving up too much long-term value for a short-term boost. Their Wednesday night acquisition of Mike Montgomery gives them a quality lefty to stick in their bullpen, and relieves some of the pressure to pay the going price for Miller, though, of course, I’m sure they’d still love to have him. But it seems they’d like to acquire him while retaining Schwarber, preferring to have both on next year’s roster as they make perhaps their final run with Jake Arrieta at the front of their rotation.

But if the Yankees hold fast, and say it’s Schwarber-or-nothing, are the Cubs wisely protecting their future, or passing up an opportunity to increase the odds of bringing Cubs fans their first World Series title since 1908? Well, it all depends on what you think Kyle Schwarber is going to turn into.

Most of the discussion surrounding Schwarber’s value has been tied to his defensive value, or lack thereof. A fringy catcher, the Cubs appeared to settle on him as a left fielder, believing he was athletic enough to be a reasonable defender out there, even if he wasn’t ever going to be an asset in the field. Those who were optimistic about his defense out there saw a potentially average glove, and if he was an average defensive left fielder, he’d be a valuable player indeed, given his offensive skills.

But from my perspective, the conversation about Schwarber’s defensive questions have perhaps overshadowed the fact that we shouldn’t be entirely certain that Schwarber is going to be a great hitter.

Schwarber was certainly impressive in his debut last year, running a 131 wRC+ in the regular season, then mashing his way to a 249 wRC+ in the postseason. Putting the two together — since there’s no reason to ignore his postseason performance — Schwarber put up a 143 wRC+ during his rookie year. For reference, Kris Bryant has a 139 wRC+ during his time in the big leagues (postseason included), so yeah, it’s easy to see why Schwarber got the entire city excited about what he could do at the plate.

But when we look under the hood a little bit, I think there are reasons to believe that Schwarber will have a tough time repeating his 2015 success at the plate over a larger sample.

For instance, I think his contact rate presents a legitimate area that will require improvement if Schwarber is going to become the kind of hitter the Cubs are hoping he will be. Last year, Schwarber made contact on just 67% of his swings, and perhaps more importantly, only 75% of his swings on pitches in the strike zone. It’s perfectly normal for a young hitter to chase pitches out of the zone early in their career, then learn the strike zone and make adjustments as they get older, so low out-of-zone contact rates aren’t as concerning, but swinging and missing at pitches in the zone is a more challenging correction.

Dating back to 2008, there have been 620 player-seasons in which an age-25-or-younger hitter has come to the plate at least 250 times. Of those 620 player-seasons, Schwarber’s 2015 in-zone contact rate ranked 614th, so this wasn’t just your run-of-the-mill low-contact rate for a young power hitter. The only players who had posted lower in-zone contact rates during a season? George Springer, Mark Reynolds, Chris Davis, Jon Singleton, and Oswaldo Arcia. Chris Carter was a few tenths of a percentage point ahead of Schwarber, and Justin Upton wasn’t far off either, but if you keep going up the list, you see Mike Olt, Mike Zunino, Joc Pederson, Junior Lake, Wladimir Balentien, and Michael Taylor.

These are the kinds of young hitters that struggled to make contact on pitches in the zone at a similar rate to Schwarber. And if you look at how they developed after putting up those marks, it’s not necessarily a super encouraging group.

Low Contact Hitters Player Low Z-Contact% Career Z-Contact% Career wRC+ George Springer 70% 76% 126 Mark Reynolds 70% 74% 103 Chris Davis 72% 78% 121 Jon Singleton 72% 72% 79 Oswaldo Arcia 73% 75% 100 Chris Carter 75% 76% 111 Justin Upton 76% 81% 120 Mike Olt 76% 74% 60 Mike Zunino 76% 78% 73 Chris Davis 76% 78% 121 Joc Pederson 76% 79% 113 Junior Lake 77% 80% 81 Wladimir Balentien 77% 78% 69 Michael Taylor 77% 78% 71 Matt Joyce 77% 84% 114 Wilin Rosario 77% 83% 94 Jackie Bradley Jr. 78% 82% 93 Kris Bryant 78% 79% 141 Avisail Garcia 78% 83% 87 Elijah Dukes 78% 83% 110

Those are the 20 hitters who posted a Z-Contact% below 78% in a 25-or-younger season since 2008. As you can see, most of them did improve their in-zone contact rates, with George Springer, Chris Davis, and Justin Upton making the biggest leaps forward, each getting their career Z-Contact% up five or six percentage points over their lowest single-season mark. The overall average was a three percentage-point improvement, we should expect Schwarber to make more contact as he develops.

But also note that, of the 20 hitters on that list, there’s exactly one guy who might be considered a great hitter: Kris Bryant. Davis and Upton have had a couple of great seasons at the plate, but overall, they’ve been more good hitters than great hitters. Starting from a base this low in terms of in-zone contact rate means that Schwarber probably can’t be expected to become more than an average hitter for contact, even with future development, and that puts a lot of pressure on his contacted balls to produce value to make up for all the swings and misses.

Now, it’s easy to just look at Bryant and say “hey, we’ll take a left-handed Bryant, no problem.” And certainly, if Schwarber could do anything close to what Bryant can do at the plate, he’d be a franchise cornerstone, even with the defensive question marks. But there’s one pretty big difference between Schwarber and Bryant: handedness.

Schwarber is a left-handed hitter, which means teams can and will aggressively align their defenses to combat his pull tendencies. As a lefty who pulled 47% of his balls in play as a rookie, Schwarber was an obvious shift candidate, and as such, he saw three defenders on the right side of the bag in 62% of his plate appearances last year. Bryant is also a bit of a pull hitter (though less extreme than Schwarber, at 44% for his career), but as a right-hander, he’s simply more difficult to defend, since teams aren’t as willing to put three players on the left side of the infield; Bryant has only hit with the shift on in 36% of his plate appearances.

As such, Bryant has been able to run a .355 BABIP in his first year and change as a big leaguer; it’s one of the primary reasons he’s been such a good hitter even with an above-average strikeout rate. But that is just an unreachable level for Schwarber; left-handed pull-hitters simply don’t run BABIPs that high in this day and age of defensive positioning.

Go look at the normal range of BABIPs for high-pull lefties over the last three years. Even the guys who hit the ball the hardest — guys like Chris Davis, David Ortiz, and Anthony Rizzo — now run BABIPs in the .280 to .290 range. These are the guys the shift is designed to do the most damage to, and Schwarber is going to be part of the group that is most hurt by modern defensive positioning. Not surprisingly, even though he hit the ball very hard last year, Schwarber ran just a .293 BABIP, and we probably shouldn’t expect much of an increase from that.

But, of course, we’re not saying Schwarber’s 2015 BABIP was an unsustainable fluke, and he was a good hitter while getting shifted last year, so who cares? Well, that’s true to an extent. But there is one part of Schwarber’s 2015 batting line that we probably shouldn’t expect to continue, and it was one of the main reasons he was so productive last year; he had an absurdly high percentage of extra base hits clear the fence.

Postseason included, Schwarber hit 21 home runs last year, but only six doubles and one triple, so 75% of his extra base hits were home runs. That’s why Schwarber had a .273 ISO, just a tick shy of Giancarlo Stanton’s career .274 mark. Except no one, not even Stanton, has ever shown that they can turn that rate of well-struck balls into home runs.

Over the last 10 years, in fact, no player has even managed to put up a HR/XBH rate of even 60%. Among qualified hitters, the highest percentage of extra base hits to go for home runs from 2007-2016 belongs to Adam Dunn, at 59%. Jim Thome comes in at 58%, then you have Russell Branyan and Chris Carter at 57%, Jason Giambi at 56%, and Alex Rodriguez at 55%. The modern super-sluggers, Stanton and Davis, are both at 54%. These are the kings of old player skills, the three-true-outcome stars who swing for the moon on every pitch, and they’re all showing that having 60% of your extra base hits go for home runs is a practical limit.

So, realistically, Schwarber isn’t going to keep getting so many of his extra base hits to go over the fence. If you give him a still-top-of-the-slugger-chain 55% HR/XBH rate, then he would distributed his 2015 extra base hits as 12 doubles, one triple, and 15 home runs, instead of 6/1/21. Just that change would have cost him 12 total bases from last year, knocking his slugging percentage down by 50 points, and that’s with an optimistic view of his power output, putting him in the same class as guys like Stanton and Davis.

Stacking up all these potential concerns, and I think it’s reasonable to be a little skeptical of the idea that Schwarber is definitely going to develop into an elite hitter. Left-handed pull hitters with low contact rates need to be monsters when they hit the ball, and Schwarber’s extra base hit profile simply leaned too heavily to the home run side of things to be sustainable long-term. Take away a few of those homers, and now the skillset is starting to look more like Mike Napoli.

There’s definitely nothing wrong with Mike Napoli. He’s had a very nice career, putting up +27 WAR as a slugging C/1B. And his walk, strikeout, and ISO rates look right in line with reasonable projections for Schwarber’s future. As a right-handed hitter, he’s been able to run a .308 career BABIP, which might be a bit higher than we should expect from Schwarber, but something in that 120 to 125 wRC+ looks about right, based on the things he does well and his areas of weakness.

That’s a good hitter. That’s a guy you want in your line-up. But as a guy who still does have questions about his eventual defensive value, and is coming off knee surgery, Schwarber’s upside looks a bit limited to me. Could he start hitting for a lot more contact and hit 40 bombs a year? Sure, anything is possible; Jose Altuve is a slugger now, after all. But should we expect it? I don’t think so, not based on what we know right now. And if he’s a defensively-challenged, good-not-great hitter, he’s probably worth something like +1 to +3 WAR per season, depending on what the defense turns out to be.

Now, that brings us to the inevitable question of his value compared to that of Andrew Miller. After all, we can’t talk about Schwarber’s shortcomings without mentioning that Miller can only face six or seven batters per game before he has to be removed. Given the fickle nature of relief pitching, it’s not like Miller is a franchise player either, and it’s easy to see why the Cubs might not want to give up five years of a potential above-average everyday player for two and a half years of a reliever. After all, if Schwarber is even just an average player, you’re giving up something like +10 WAR in future production, and the Cubs would be lucky if Miller gave them +5 WAR over the next two-and-a-half years.

But we also need to factor in the discount that has to be put on future value compared to present value. Especially for a team like the Cubs, wins today are worth a lot more than wins in 2021, and given that Schwarber has the kind of skillset that gets overpaid in arbitration, he might not actually be much of a value in four or five years anyway.

How much you want to discount future wins is far more art than science, and will be different for every team. For an organization like the Cubs, with a real chance to win the World Series for the first time in 108 years, I think you have to put a pretty significant discount on future wins. So, just for the fun of it, here’s what Schwarber and Miller’s future value to Chicago might look like if we discount future WAR by 20% each year.

Projected and Discounted WAR Miller Projected WAR Discounted WAR Schwarber Projected WAR Discounted WAR 2016 1.0 1.0 2016 – – 2017 1.5 1.2 2017 2.5 2.0 2018 1.0 0.6 2018 2.5 1.5 2019 – – 2019 2.0 0.8 2020 – – 2020 1.5 0.3 2021 – – 2021 1.5 0.3 Total 2.8 4.6

With a 20% discount rate — which is entirely subjective, of course, so this more for illustration than a precise valuation — a +10 to +3.5 WAR gap in favor of Schwarber during their relative control years shrinks down to a +4.6 to +2.8 WAR gap. It’s still not enough to overcome the long-term value that Schwarber provides, but it’s at least an argument that it’s not insane for the Cubs to consider a deal involving those two, especially if the Yankees sweetened the pot.

Like, say, adding Aroldis Chapman to the deal. Putting Chapman and Miller in the Cubs bullpen, along with Hector Rondon and Pedro Strop, would give the Cubs the best bullpen in baseball, to go along with all the other things they’re the best at. And at that point, the short-term upgrade would be large enough that I think the Cubs would have to at least consider moving Schwarber.

I know the Cubs love his personality and his work ethic, and perhaps he will turn into the kind of franchise cornerstone that justifies keeping him for the future, even if he could bring back a serious upgrade to the team in the short-term. But given the questions I have about his offensive upside, in addition to the real questions about his defensive value, I think I’d at least be engaging the Yankees on a Schwarber-for-Miller-and-Chapman deal. Schwarber looks like a very nice young hitter, but the Cubs have other guys who also look like nice young hitters.

What they don’t have is a World Championship in the last century. Kyle Schwarber can’t help them with that this year. Andrew Miller and Aroldis Chapman could, and from my perspective, the short-term upgrade might be worth the long-term cost.