Most of the Cubs-related news from the Winter Meetings centered on the possibility of a Kris Bryant trade. I was hoping not to have to write about this, but since the rumors persist, I’m going to break down the reasons why the team’s star player is on the trading block, and estimate a possible return based on player valuation numbers.

Why would the Cubs trade Kris Bryant? If we’re being generous, the argument goes like this:

Bryant probably wants to test free agency, and the Cubs and Scott Boras have been unable to agree on an extension. He’ll be going into his age-28 season, and it seems doubtful he will repeat his MVP-level 2016. Bryant has suffered nagging injuries in both of the previous two seasons, and while he doesn’t seem fragile, he hasn’t proven to be super durable. Trading Bryant now would maximize his value and allow the Cubs to get players in return that would allow them to still compete in 2020 and protect them against falling off a cliff after 2021. The team could then reinvest the money saved by trading Bryant in a reliable starting pitcher and a couple of bullpen arms.

However, the uncharitable argument paints a much bleaker picture:

The Ricketts family desperately needs to cut payroll after their Wrigleyville renovations exceeded their budget by around 100%. The team suddenly doesn’t have as much money as they expected, and can count on Cubs fans to still attend games, especially after they won the World Series in 2016. They’re not willing to meet Bryant’s asking price on an extension, and figure they can save over $40M by trading their best player.

The uncharitable argument isn’t likely to win over any fans, and while it is certainly possible that’s the reason for these rumors, I don’t believe it’s particularly compelling, so I’m going to focus on the generous argument here. Initially, I was somewhat persuaded, but if teams value players in the same way that public analysts do, I don’t think the return for Bryant would be anything close to satisfying for most Cubs fans.

To estimate a potential Kris Bryant trade, we first have to get into some baseball evaluation math. Note: for the purposes of this article, I’m going to assume that Bryant loses his service time grievance, and thus remains under team control through 2021.

On the free agent market, one win above replacement is currently estimated to be worth about $9M. By combining projected WAR and projected salaries, it’s easy enough to reach a rough estimate of the “surplus value” of a player with this formula:

Surplus value = projected WAR * $9M - projected salary

According to the Steamer projection system, Bryant is projected for 4.8 fWAR in 2020. We’ll assume he’ll produce that much in 2021 as well, which would mean he would produce 9.6 wins over the next two seasons. Bryant is projected to make around $18M in arbitration in 2020, so it wouldn’t be surprising if he were to make a little over $40M over the next two years. That would mean Bryant would produce $86.4M of value and get paid $40M, giving him $46.4M of surplus value. In a more optimistic estimate, if Bryant instead returned to near his 2015-2017 levels and produced 6.0 fWAR over each of the next two seasons, he’d produce $108M of value, leaving him with $68M of surplus value.

We can use this math to evaluate current major leaguers, but evaluating prospects is a bit trickier. At FanGraphs, prospects are assigned a “future value”–“a grade on the 20-80 scale that maps to anticipated annual WAR production during the player’s first six years of service.” Last November, Craig Edwards did a study and developed a method of determining the dollar value of each prospect tier. To give a general idea of the future value scale, before the 2019 season, Vladimir Guerrero Jr. was assigned a 70 FV as the top prospect in baseball, valued at $112M. The Cubs' Miguel Amaya was the 97th best prospect in the league, with a 50 FV, valued at $18M.

There are, of course, drawbacks to this method of valuing players, the most obvious of which is that you’re assigning a dollar value to a player based on one distilled number. Different teams also value different things; the Cubs gave up a hefty package for Aroldis Chapman in 2016 because they felt he would be able to secure their first World Series victory in 108 years, while a team like the Rays with a tighter budget consistently trades good, established major leaguers for less-established players that are owed less money. However, for the purpose of this article, valuing players like this makes it easier to see what kind of return we could expect from a Kris Bryant trade.

As a reminder, we estimated Bryant’s surplus value to be $46.4M based on current projections. According to FanGraphs' prospect valuations, that would put him around the value of a 55 FV position-player prospect. That type of prospect produces, on average, 5.1 WAR, and at $9M/WAR he’d be worth $45.9M. For position players, that ranges from 15th in the top 100 all the way down to 36th. Looking at FanGraphs' prospect rankings, the Braves' center-field prospect Drew Waters fits into this tier, and he would certainly be a compelling target for the Cubs. Alternatively, it’s possible that the Cubs would instead trade for two prospects of lesser value, in order to spread their risk among multiple players. You could combine a 50 FV position player ($28M, 38th-104th) and a 50 FV pitcher ($21M, 44th-106th) to get to $49M, about what Bryant’s surplus value is. That’s a position player around Nico Hoerner’s level, and a pitcher like the Braves' Kyle Wright.

In our optimistic valuation of Bryant ($68M surplus value), he could be worth a 50 FV pitcher ($21M) and a 55 FV position player ($46M), a package like Drew Waters and Kyle Wright. I think that’s probably close to a best-case scenario for a Bryant return, at least based on the standard math. In this scenario, the Cubs could instead go all in on one 65 FV player they really liked, someone who would be one the top ten prospects in baseball. Still, even if the Cubs got someone like Jo Adell from the Angels (and I doubt they’re still in the running for Bryant), even Bryant’s somewhat-pessimistic projection of 4.8 WAR is a near-best-case scenario for prospects. There’s always the possibility that Adell becomes one of the best players in baseball, and in that case the trade would be well worth it, but with non-established players, Bryant’s consistent production is on the far-positive side of the distribution of outcomes.

Even though it felt like Bryant had a bit of a down year in 2019, he was the most valuable player on the Cubs, and the 24th-best position player in baseball by WAR, practically tied with Juan Soto. It’s important to keep in mind that the reason prospects are valued so highly is because of the much-vaunted “financial flexibility” they provide, not necessarily because of how much WAR they’ll produce. Any prospect turning into a 4.8-win player is a massive success, and if you already have a 4.8-win player and you’re trying to make the playoffs, you should keep him.

If the Cubs were in the Dodgers' position in their division, trading Bryant might be more acceptable, but this isn’t a team with wins to spare. While the underlying numbers suggest they were better than a third-place team in 2019, they still finished in third place. If the Cubs won’t reinvest the money they save from a Kris Bryant trade in the team (and it doesn’t seem like they would), it’s difficult to imagine a scenario in which the move makes the team better in 2020, and if the team isn’t willing to invest money in making the 2020 team better, then they may as well trade other players as well.

It feels like you would be hard-pressed to find many Cubs fans who would be happy with getting Waters and Wright for Bryant, and that return is on the high end, at least according to the math above. I don’t think even the optimistic return makes sense for a team that’s trying to compete in 2020 and 2021, and the more numerically-realistic one-for-one trade of Bryant for Waters only makes sense if the front office was going to reinvest Bryant’s salary in the major league roster. Drew Waters could be a great major league player! The Cubs would definitely benefit from having him in center field. But it’s unlikely he’ll produce 10 WAR over the next two seasons. Trading Kris Bryant for a mathematically-reasonable package would hurt the Cubs' chances of winning in each of the next two years, and not substantially increase their odds in the following years. It’s easy enough to avoid this problem: don’t trade Kris Bryant.