As the offseason has begun so have rumors that the Cubs are open to trading pretty much anyone on their roster. Let me preface this by saying that I don't think the team should need to trade any of their core players. The Cubs should be able to afford to keep their core intact past their arbitration years and into free agency. But, like with many big-market teams around baseball, it seems the front office is under a mandate to decrease salary and make more longer-term moves. Assuming this is the case…
Trading Bryant would be incredibly difficult. Teams know he's likely to want to test free agency, and he's projected to make around $40M over his final two years of arbitration. The front office would need to find a team that's willing to pay Bryant's salary and give up several top-tier prospects for him. With Bryant's nagging injuries over the past two years, it seems like many teams would balk at the Cubs’ asking price, instead opting to sign Anthony Rendon or Josh Donaldson without giving up any prospects.
While trading Rizzo would make sense in that Bryant and Caratini have both played first well in his absence, it would be aggressive to trade a clubhouse leader right after hiring a rookie manager. I'm not necessarily a fan of giving Rizzo a huge extension since he'll be a 32-year-old first baseman with back issues, but I'm fairly certain the Cubs will keep him around until then, and maybe for the rest of his career.
The Cubs could trade Javier Báez, but he seems to be the most likely candidate out of the core four (Contreras, Báez, Bryant, and Rizzo) to sign an extension. He's blossomed as a shortstop the past two seasons and provided the second-most Fangraphs WAR on the team despite dealing with a couple injuries which affected his performance.
I'm sure the Cubs are open to trading Kyle Schwarber, but I doubt they would be able to get a return large enough that would make them comfortable doing so. There are other defensively-limited corner outfielders on the free agent market, and I would expect the Cubs to value Schwarber's scorching-hot end to the season more than other teams. It doesn't help that there aren't many competitive American League teams that are looking for a designated hitter, where his value would be highest.
This leaves Willson Contreras. There are a couple of teams that could use a catcher (besides the Reds and the Brewers, who don't seem like likely trade partners). Contreras is one of the best offensive catchers in baseball, and has a great arm behind the plate. Concerns about his framing and hamstring injury concerns are the main things that would decrease his trade value, but there are signs that he improved his framing in the second half of 2019.
This seems the most likely to me. The Rangers and Cubs have a history of making trades under these front offices, and the Rangers currently have the worst catching in baseball as it stands. They'll be opening a new stadium, too, so maybe they'll want to make a splashy trade in addition to any free agent acquisitions. Jeff Mathis (star of this tweet) got entirely too much playing time last season for the Rangers. Fangraphs ranks their farm system just ahead of the Cubs’. Possible trade candidates include:
2B/3B Nick Solak — Acquired from the Rays for a low price likely due to their 40-man roster crunch. Fangraphs ranks him as the organization's top prospect (104th in the MLB). Solak could be an interesting Ben Zobrist replacement, though if he primarily played second base Nico Hoerner would have to move to center field. In 33 games with the Rangers, he slashed .293/.393/.491 for a 126 wRC+.
RP José Leclerc — A very good reliever with a team-friendly contract (with two club options in 2023 and 2024). Leclerc had a much worse 2019 than 2018, but still put up 0.4 more fWAR than any Cubs reliever.
RP Emmanuel Clase — A young fireballing reliever with natural cutting action on his fastball. Clase doesn't have much of a major-league track record, but he's the type of reliever that the Cubs have failed to develop under Theo Epstein.
Lance Lynn had one of the best seasons of any pitcher in 2019, but with two more cheap years on his contract it seems unlikely that the Rangers would want to trade him. Mike Minor had a nice season but ended up with a FIP only .01 less than Jon Lester. Combined with the fact that he only has one year left on his contract, I would guess the Rangers value him more highly than other teams do. The Rangers also have a couple of starting pitchers in their farm system, but they're riskier types, and don't seem like a great match for this trade.
The Rays lost catcher Travis d'Arnaud to free agency, and they have the highest-ranked farm system in baseball according to Fangraphs. Potential trade targets here include a whole swath of bullpen arms that would appeal to the Cubs, as well as some less-traditional starters in the minors. If the team was willing to part with one of their “bulk guys” like Ryan Yarbrough or Yonny Chirinos in addition to one of their lower-leverage relievers like Oliver Drake, the Cubs would surely be interested, though I can't tell how much the Rays are willing to give up.
I don't particularly want to see Contreras on the Astros, but they did just lose both their catchers to free agency. I see the Astros as a less-likely fit mainly because they're a more plausible opponent for the Cubs in the playoffs in the next two years (though the Rays aren't far behind), and their farm isn't quite what it used to be. Catcher is one of the main holes in their roster, though, and any pitchers they did give the Cubs wouldn't be too difficult for their player development machine to replace. However, I doubt the Astros would give up top pitching prospect Forrest Whitley for Contreras, even after a down year. I'm sure World Series phenom Jose Urquidy would intrigue the Cubs, but after such a successful major league debut and Gerrit Cole departing in free agency it seems unlikely that the Astros would be willing to part with a promising young starter.