Among the more interesting subplots of the upcoming offseason, aside from "who will sign Anthony Rendon and Gerrit Cole," and "what will Yankees fans do if their team doesn't sign Anthony Rendon or Gerrit Cole," is what's happening -- or about to happen -- in Boston. Will J.D. Martinez opt

Among the more interesting subplots of the upcoming offseason, aside from "who will sign Anthony Rendon and Gerrit Cole," and "what will Yankees fans do if their team doesn't sign Anthony Rendon or Gerrit Cole," is what's happening -- or about to happen -- in Boston.

Will J.D. Martinez opt out? Will Mookie Betts get traded? And what will the impact of new "chief baseball officer" Chaim Bloom, who was introduced Monday, be in all of this?

• Bloom doesn't tip hand about plans for Betts

It's the second one of those questions, the idea of trading Betts, that stands out the most. He's 27 years old, he's a World Series champion, a three-time Gold Glove Award winner, a Most Valuable Player Award winner and it was just one year ago that he was finishing up one of the most historically great seasons in Red Sox history.

Over the last four years, the Wins Above Replacement leaderboards look like this:

34.9 WAR -- Mike Trout

30.7 WAR -- Mookie Betts

25.4 WAR -- Christian Yelich

24.2 WAR -- Anthony Rendon

23.2 WAR -- Francisco Lindor

These kinds of players simply don't appear on the market very often, because when teams have them, they tend to keep them. (This is obviously the best outcome for Red Sox fans: That Bloom and friends do, in fact, keep him.) When one does, every team in baseball ought to stand up and take notice, to the point that this article could and should look like this:

"A list of teams who should be interested in Mookie Betts:

All 29 other teams should be interested in Mookie Betts."

Right. That.

But OK, that's not really going to happen. The Red Sox would never trade him to the Yankees, for one, and since he's got only a single year remaining before he's a free agent, a handful of teams that aren't likely to contend in 2020 wouldn't make the effort to get him. A few other teams that probably would like him may not have the prospects to do it, or may have larger needs to fill than in the outfield.

The thing is, it's pretty difficult to find a historical reference for a trade like this. Over the last few years, a handful of stars have been dealt with one year remaining before free agency, but none of the hitters like Paul Goldschmidt (2018-19 from D-backs to Cardinals), Andrew McCutchen (2017-18 from Pirates to Giants), Jason Heyward (2014-15 from Braves to Cardinals), Justin Upton (2014-15 from Braves to Padres) or Matt Holliday (2008-09 from Rockies to A's) were as young, productive and valuable as Betts is, making them imperfect test cases.

We've had big stars getting traded with half a season remaining for underwhelming returns, like Manny Machado (2018 from Orioles to Dodgers), Josh Donaldson (2018 from Blue Jays to Indians), J.D. Martinez, (2017 from Tigers to D-backs) or Holliday (2009 from A's to Cardinals). We've had outfielders on low-cost, long-term contracts get traded and get better (Yelich, 2017-18 from Marlins to Brewers), and we've had them get traded and decline (Adam Eaton, 2016-17 from White Sox to Nationals).

But we've never really had this, a player this young and productive and with only one year left before free agency being available. That makes it incredibly difficult to know what kind of trade package in return is realistic, because the list of comparables is, basically: ___.

(For example: When Arizona traded Goldschmidt last winter, it got three players, including a starting catcher in Carson Kelly and a solid starter in Luke Weaver. But Goldschmidt was older than Betts and less productive, yet his next-season salary was also half as much. That's why this all gets so complicated.)

And while it's possible that a team could trade for Betts and then sign him to an extension, as St. Louis did with Goldschmidt, Betts has made it clear that he intends to at least test out the free-agent market, so any acquiring team couldn't assume more than 162 regular-season games of his services.

Here's what you really need in a match for Betts:

1) A team either already good enough to contend in 2020 or at least close enough that Betts would make them a contender right away.

2) A clear need in the outfield.

3) The ability to satisfy Boston's needs in prospects or taking on contracts.

4) The ability to take on the estimated $28 million or so Betts will get in 2020.

5) Isn't the Yankees or Rays, because come on. It won't be the Yankees or Rays.

That means that any deal would probably be deemed "too much" from fans of the team that acquires him -- it's only one year! his contract is high! -- and "not enough" from fans of the Red Sox -- it's literally Mookie Betts! Good times all around.

That ought to cut our list of possible trade targets down considerably, and you could go either way on teams like the Astros (they already have outfielders Michael Brantley and Josh Reddick headed into free agency after 2020, and George Springer after that) and the Brewers (they have larger needs on the mound than outfield, and a weak farm system; this applies also to the Angels, who would never include top prospect Jo Adell for one year of Betts).

The best outcome for the Red Sox is obviously just "keep Betts and sign him to a long-term contract," and that may yet be the outcome. But in case they don't ...

A list of 6 possible trade partners for Betts

Let's split this into two groups of three teams apiece, first teams that made it to October this year and want to go further, then teams trying to boost themselves into next year's playoff tournament. These aren't the only six teams, of course. Just maybe the most interesting ones.

The teams that already made the playoffs in 2019

1) Dodgers

What's the only thing more painful than losing the World Series two years in a row? Losing in the NLDS the next year to a team that won 13 fewer games than you did. The Dodgers' window is hardly closing, and even if they did absolutely nothing this winter, they'd still be the heavy favorite to win their eighth consecutive division title. But that's not good enough, is it?

If the Dodgers aren't going to spend to acquire Rendon or Cole -- which they absolutely could afford to do, it just hasn't been their style to do so -- trading for one of the best players on earth to reinforce their lineup would certainly be a nice consolation prize. Imagine, if you would, an outfield with Betts alongside potential NL MVP Cody Bellinger.

The Dodgers have a Top 3 farm system; they've preferred to spend high dollars on short contracts than longer-terms ones; and they've shown urgency to make win-now trades in the past for Machado and Yu Darvish. This fits all around.

Possible key pieces: Minor League catcher Keibert Ruiz (No. 3 per MLB Pipeline); outfielders Alex Verdugo or Joc Pederson; pitchers Kenta Maeda, Josiah Gray (No. 4), or Tony Gonsolin (No. 6)

2) Braves

Atlanta's back-to-back October losses -- and 10 straight playoff series -- don't quite rise to the frustration levels of the Dodgers, but the fit is just as good. The Braves might lose Donaldson to free agency, and they have a pretty obvious spot open next to Ronald Acuña Jr. in right field, where Nick Markakis' five-year run of being generally OK (he was almost exactly league average as a hitter with the Braves) is likely at an end.

The Braves also have a strong farm system, and Betts' 2020 salary would almost exactly replace what Donaldson earned this year; it would also buy outfield prospects Drew Waters and Cristian Pache a few more months to develop. It won't be easy to hold off the Nationals and Phillies again in 2020, and then you still have the Dodgers to get through in the playoffs. Better have Betts on your side than have to face him.

Possible key pieces: Outfield prospects Waters (No. 1) or Pache (No. 2); one of the many Atlanta pitching prospects; perhaps veteran outfielder Ender Inciarte if the Red Sox are also moving on from Jackie Bradley Jr.

3) Cardinals

If the NLCS debacle against the Braves proved anything, it's that the St. Louis offense isn't strong enough, and it could get even weaker if Marcell Ozuna departs via free agency. If he does, the current outfield depth chart is some combination of Dexter Fowler, Harrison Bader, José Martínez, Lane Thomas, Randy Arozarena, Tyler O’Neill, Dylan Carlson, Tommy Edman and Yairo Muñoz. There's a lot of talent in there, and maybe you can cobble together a decent group from it, but there's no one in there who comes close to approximating what Betts brings.

Possible key pieces: Some of those outfield prospects; Martínez has always been an AL player

OK, what about the teams that didn't see October games this year?

The teams that want to get into the playoffs in 2020

1) Mets

We'll admit that it's expected to be unlikely for the Mets to take on Betts' contract, especially because Jacob deGrom's salary nearly triples from $9.5 million to $25.5 million, but they also find themselves in a tough spot: How do you stomach trading top prospects for Robinson Cano and Edwin Diaz, then more for Marcus Stroman and then not keep trying to win right now?

In addition to adding another elite bat to an offense that was quietly pretty good, Betts could spend the season in center field between Michael Conforto and Brandon Nimmo, helping to clean up the porous defense that was one of the biggest reasons the Mets missed the playoffs in 2019. There's an intriguing fit between the two sides given that in first baseman Dominic Smith (blocked by Pete Alonso) and bat-first player J.D. Davis, the Mets have a pair of talented hitters without obvious defensive homes.

This would also open up everyone to endless "Mookie Betts on the Mets" headlines, which would be delightful ... at first.

Possible key pieces: Smith; LF/3B-but-really-a-DH Davis; shortstop prospects Ronny Mauricio (No. 1) or Andres Gimenez (No. 3)

2) Reds

Somewhat similarly, the Reds made some win-now moves over the last year -- Alex Wood, Yasiel Puig, and Matt Kemp from the Dodgers, starters Sonny Gray and Tanner Roark from the Yankees and Nationals, respectively, and then Trevor Bauer from Cleveland this summer -- that were generally well-received as an all-too-rare occurrence of a team trying to get better in the present.

The problem was, the Reds didn't get better, or at least not good enough. It's true that they avoided 90 losses for the first time since 2014, but they still finished 75-87, were never really in playoff contention, and shipped out prospects Jeter Downs, Gray, Taylor Trammell, Tanner Rainey and Shed Long in the process. They're not exactly an "all-in" team, but with a strong pitching staff and not enough offense, they can't really stop now, either. Imagine Betts in center between Jesse Winker and Aristides Aquino, with Nick Senzel moving back to second base? Reds fans are asking about it, and Cincinnati management has said it expects to increase payroll this winter.

Possible key pieces: No one from the Major League roster, so pick some Minor League names of interest

3) Padres

It's been nine straight losing years in San Diego, despite big contracts for Machado and Eric Hosmer, and the Padres can't simply wait around for the Dodgers to stop being good. (They also have only one more year left of closer Kirby Yates, arguably 2019's most dominating reliever.) A hopefully fully healthy year of Fernando Tatís Jr. should help, and they should absolutely be in on any and all of the big free-agent starting pitchers, but the Padres need to convert all that "quantity" in their outfield into "quality," especially since an age-30 Hosmer offensive breakout seems unlikely to come.

Possible key pieces: Outfielders Hunter Renfroe, Manuel Margot, Franchy Cordero; pitching prospects Adrian Morejon (No. 7) or Michel Báez (No. 9); Major League pitcher Joey Lucchesi; the more prospects the Padres pour in, the more likely it is they could entice Boston to take back Wil Myers

Mike Petriello is an analyst for MLB.com and the host of the Ballpark Dimensions podcast.