A Buyer’s (And Seller’s) Guide To The MLB Trade Deadline

For most Major League Baseball teams, the trade deadline is a chance to step back and take stock of the franchise’s trajectory. Although only a small fraction of rumored deals actually end up happening, a team’s willingness to swap assets — as either a buyer or a seller — says a lot about where it is in the cycle between contending for a World Series and playing for the future.

For a few teams, the choice has already been made. These are the clubs on the ends of the baseball spectrum: the bottom dwellers already committed to punting the present in order to stockpile young talent and the clear front-runners who can begin fine-tuning their playoff rosters in July.

But the bulk of the league faces a fork in the road and doesn’t have the luxury of soul-searching with the trade deadline less than two weeks away. The decision to buy or sell is both critical — botched maneuvers can cripple a franchise for years — and further complicated by whether teams are getting a “rental” player (with an expiring contract) or someone who can help them for the next few years. But fear not, baseball general managers, we are here to help.

A few years ago, my colleague Nate Silver and I developed a statistical framework for trade-deadline strategy: the Doyle Number (named for a certain pitcher the Detroit Tigers mortgaged their future to acquire at the 1987 deadline). Doyle represents the number of future wins a team should be willing to part with in exchange for adding an extra win of talent this season. So a Doyle of 1.00 means a team should be indifferent to buying or selling — a one-win improvement this year adds as much to its current World Series odds as a future win would add over the long term.³⁹ If its Doyle rises any higher, it should probably be buying (since wins this year are more valuable than future wins); any lower, and it should be selling.

For example, the Cleveland Indians currently have a Doyle Number of 1.48. With a good (though not quite great) roster and decent (but not quite ironclad) division-series odds,⁴⁰ they should probably be trying to add talent over the next few weeks to bolster their chances of returning to the World Series. Meanwhile, the New York Mets’ Doyle is 0.08; their injury-riddled talent base is mediocre, and they have very little shot at the division series, so they should be selling off anyone that isn’t nailed down.

With those ground rules in place, here’s every team’s Doyle number as of July 16:⁴¹

The Doyle topples one of the most common perceptions of the deadline: The team most in need of a trade is the team that is one bat (or one arm) away from making a postseason run. By contrast, Doyle shows that the the teams who should be most willing to buy are the teams having the best seasons — not teams merely on the cusp of the playoffs. It’s a consequence of how random the MLB playoffs are: When even the best teams have long odds of winning, there’s practically no amount of talent a team can add that will cause its World Series probability to hit diminishing returns.

This year, the top Doyle teams are the historically dominant Los Angeles Dodgers and Houston Astros — and, to a lesser extent, the Indians, Washington Nationals and Boston Red Sox. With the possible exception of Houston, each team has at least one position where it can substantially improve, and Doyle indicates they should focus on shoring up those weaknesses in preparation for a World Series run.

More interesting, however, are the clubs near the threshold between buying and selling. These are teams for whom there is less of a clear-cut direction to take — but some decision must be made, since any direction would add more total future championships than merely standing pat. One archetype for that group is the unexpected contender: Think of the Milwaukee Brewers, who find themselves in first place in the National League Central division despite a relatively unimpressive collection of talent. Milwaukee’s 1.26 Doyle suggests it should lean toward buying, since an improved core will become much more valuable in the postseason.

The opposite model might be that of Milwaukee’s division rival, the Chicago Cubs: an expected favorite to whom Doyle gives a disappointingly low World Series probability. The defending champs are having a well-documented down year, and although they’re talented enough to have decent title odds if they make the playoffs, that’s far from guaranteed no matter what deadline moves they make. As a result, their 0.66 Doyle suggests they should lean toward punting on this season.

The Cubs, however, don’t seem willing to give up just yet, trading for starter Jose Quintana last week. They weren’t necessarily wrong to do it, either; it’s important to remember that the Doyle Numbers above mostly apply to rental players. After I tweaked the model to account for the remaining years on Quintana’s contract,⁴² Chicago’s Doyle for this specific trade became 1.31 — meaning it was probably worth it to give up top prospects in exchange for improving its talent base over multiple seasons.

Those are exactly the kinds of extenuating circumstances a team in Chicago’s current situation needs in order to justify buying instead of selling. Any team with a Doyle north of 0.60 or so could probably do a similar calculation, which means 11 clubs — the Dodgers, Astros, Nationals, Red Sox, Indians, Brewers, Diamondbacks, Yankees, Rays, Cubs and Rockies — could reasonably call themselves buyers this season under the right circumstances.

So we know who’s at the restaurant, and we know who’s on the menu — but what is everyone ordering? We can also use Doyle to build a trade deadline plan for each team, pairing them with players who fit a need and make sense given how realistic a club’s World Series chances are. For each of the 11 teams above, I gathered their current starters⁴³ and tracked how good each is this season, according to Tom Tango’s WARcel projections. I also pulled a list of deadline rental targets⁴⁴ from the excellent RosterResource.com, calculating their WAR talent as well. Multiplying a team’s Doyle Number by the difference in WAR talent between a rental target and its current starter at the same position, we came up with a “deadline index” that indicates how good of a match the player is for the team. After assigning duplicated targets to the team whose index for the player was highest, here are the best pairings between team needs and available players, according to Doyle:

Obviously, here are other layers of complexity involved in actually pulling off these deadline deals, including the quality of the trading team’s farm system, which of its existing players might return from injury before the playoffs, and the possibility of a contract extension with the player being acquired. But the general idea of Doyle is that it provides a flexible framework for trade-deadline decisions, based on how valuable it is to add or shed current talent with an eye on the future.

Keep that in mind as we watch whatever deals unfold over the next couple of weeks. A team’s Doyle Number is a rough guideline, the starting point for thinking about trade possibilities. What happens after that is a combination of reading the market, picking the right moment to strike and then making endless phone calls until that forgettable middle reliever is finally yours.

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