Mostly we tend to frame free-agent comings and goings in terms of additions. Our focus is understandably on the team that signs a given free agent and not as much on the team that's bidding adieu to him and his outputs. On some level, that makes perfect sense -- the only thing we think about more than the past is the future. 

On these electronic pages we'll be devoting plenty of words and time to incoming free agents, but before the ink starts flying let's make time for the outgoing side of things. Specifically, we query: How much on-field value from 2019 does each team stand to lose in free agency?

To do this, we're going to lean on Wins Above Replacement (WAR). WAR is an all-encompassing stat that attempts to measure a position player's or pitcher's total value. For position players, this means hitting, base-running and fielding are taken into account. It's measured in theoretical "wins" over and above what a readily available stop-gap player -- e.g., the bench player or the waiver claim -- is likely to provide. While WAR has its weaknesses and is something of a blunt instrument, it's the best publicly available catch-all metric around. It's also useful for purposes such as these. 

Below you'll find each MLB team ranked by how much total WAR it stands to lose on the free agent market -- i.e., by the sum of their free agents' individual WARs. Obviously, some of these losses will be mitigated or even improved upon by other signings or promotions, but as we head into the heart of the offseason you can consider these the roster debits that will need to be addressed in some manner. 

Also, in these calculations we're including only those players who had a positive WAR in 2019. Players with a negative WAR self-evidently didn't help the cause last season, and in most cases you can consider them additions by subtraction. It of course remains possible that some of these players will wind up signing with their 2019 squadrons, but they're still free agents at the moment and thus part of "potential losses" calculus. Now let's roll out all 30 teams ranked in descending order of how much they stand to lose on the market. 

Total free-agent WAR: 21.8. Positive WAR free agents: Anthony Rendon, Stephen Strasburg, Howie Kendrick, Asdrubal Cabrera, Brian Dozier, Daniel Hudson, Yan Gomes, Fernando Rodney, Tony Sipp, Ryan Zimmerman, Jeremy Hellickson. No surprise here. No other team stands to lose a duo the likes of Rendon and Strasburg, and then you throw in the productive likes of Kendrick and then their stretch-drive and postseason closer Hudson. The Nats will no doubt be angling to vigorously defend their title in 2020, but to do that they'll either need to pony up for some of these incumbents or find suitable replacements. GM Mike Rizzo has a challenging winter ahead. As you see above, more than 20 wins hang in the balance.
Total free-agent WAR: 14.5. Positive WAR free agents: Gerrit Cole, Robinson Chirinos, Wade Miley, Will Harris, Martin Maldonado, Collin McHugh, Joe Smith. Cole is obviously the big loss for Houston, as he was arguably the most dominant starting pitcher in baseball this season. Houston for some reason is operating with an eye on the luxury tax threshold, so it certainly seems likely that Cole is bound elsewhere. Given the Astros' problems with developing their young pitching, they may have to get creative to replace some of Cole's value.
Total free-agent WAR: 14.3. Positive WAR free agents: Yasmani Grandal, Mike Moustakas, Eric Thames, Jordan Lyles, Gio Gonzalez, Drew Pomeranz, Jeremy Jeffress, Tyler Austin, Cory Spangenberg. Grandal, who's in the discussion for best catcher in baseball, is the big potential loss here. He's an excellent hitter by positional standards and also a skilled defender. Last season in Milwaukee, he made 124 starts behind the plate and played in 153 games overall. Moustakas and Thames this past season combined for 60 homers, and the Brewers' decision not to exercise their $7.5 million option on Thames is borderline inexcusable.
Total free-agent WAR: 12.0. Positive WAR free agents: Michael Pineda, Kyle Gibson, Martin Perez, Jason Castro, Jonathan Schoop, Sergio Romo, Sam Dyson. Jake Odorizzi accepted the qualifying offer, which is good news for the Twins. Otherwise, they would've lost 80 percent of their primary rotation. They've still got rotation concerns, though, as this season Pineda, Gibson, and Perez combined for 84 starts.
Total free-agent WAR: 10.9. Positive WAR free agents: Josh Donaldson, Julio Teheran, Matt Joyce, Chris Martin, Dallas Keuchel, Adeiny Hechavarria, Billy Hamilton, Josh Tomlin, Francisco Cervelli. Donaldson is the big potential loss here, what with his power, patience, and plus defense at the hot corner. It's possible he'll return to Atlanta, but they'll have to pay the going rates. Teheran and Keuchel would be hits to the already somewhat unsettled rotation. They've already added Will Smith to the plus side of the ledger for 2020 and beyond.
Total free-agent WAR: 10.2. Positive WAR free agents: Brett Gardner, Edwin Encarnacion, Cameron Maybin, Didi Gregorius, Austin Romine, David Hernandez, Corey Gearin, Dellin Betances. Given their roster depth, the Yankees' situation isn't as pressing as those 10 lost wins might suggest.
Total free-agent WAR: 7.9. Positive WAR free agents: Homer Bailey, Brett Anderson, Tanner Roark, Jake Diekman. Think of Oakland as "Twins Lite" when it comes to rotation hits. Bailey, Anderson, and Roark accounted for 54 starts in 2019.
Total free-agent WAR: 7.5. Positive WAR free agents: Zack Wheeler, Todd Frazier, Brad Brach, Joe Panik. Wheeler is the concerning loss here, especially if those near-ubiquitous Noah Syndergaard trade rumors are finally realized. Additional rotation depth should be on GM Brodie Van Wagenen's shopping list.
Total free-agent WAR: 6.9. Positive WAR free agents: Hyun-Jin Ryu, Russell Martin, Rich Hill. Ryu and Hill accounted for 42 starts last season, which is part of why the Dodgers may be angling for starting pitching this winter. Ryu finished second in the NL Cy Young balloting, so his innings won't be easily replaced.
Total free-agent WAR: 6.7. Positive WAR free agents: Nick Castellanos, Cole Hamels, Brandon Kintzler, Ben Zobrist, Steve Cishek, David Phelps. Castellanos was wildly productive after being acquired from the Tigers at the deadline, and Hamels was a rotation asset across 27 starts. A roster makeover is likely in order for the Cubs, but a big payroll increase likely isn't.
Total free-agent WAR: 6.3. Positive WAR free agents: Madison Bumgarner, Will Smith, Pablo Sandoval, Stephen Vogt. The Giants are headed into a rebuild phase, at least for the near- to mid-term, which means they're not particularly worried about outgoing value. Losing franchise icon Madison Bumgarner will surely sting a bit, but that path forward for the Giants has already been mapped. Smith has already signed with the Braves.
Total free-agent WAR: 6.0. Positive WAR free agents: Eric Sogard, Avisail Garcia, Travis d'Arnaud. The Rays operate with an allergy to investing in the on-field product, so these losses will almost certainly be addressed from within.
Total free-agent WAR: 5.6. Positive WAR free agents: Rick Porcello, Andrew Cashner, Brock Holt, Mitch Moreland. The Red Sox are (unwisely) pivoting toward a more cost-effective roster, which probably translates into missing the postseason again. There's some talk of re-upping with Porcello, which makes some sense. The real story is whether the Sox under new GM Chaim Bloom will make the mistake of trading Mookie Betts.
Total free-agent WAR: 5.4. Positive WAR free agents: Jason Vargas, Brad Miller, Corey Dickerson, Juan Nicasio, Sean Rodriguez, Mike Morin, Tommy Hunter, Nick Vincent. The Phillies invested heavily in contending last season, and they're poised to do so again in advance of 2020. Given better health and targeted additions on the free-agent market (including, possibly, Gerrit Cole), the Phillies won't much miss any of the names above.
Total free-agent WAR: 4.2. Positive WAR free agents: Alex Avila, Jarrod Dyson, Wilmer Flores, Yoshihisa Hirano. The D-Backs were relevant last season despite some rebuilding-type moves. They could be fringe contenders again in 2020, but the names above won't have much to do with it either way.
Total free-agent WAR: 3.4. Positive WAR free agents: Yasiel Puig, Jason Kipnis, Tyler Clippard, A.J. Cole, Tyler Olson, Cody Anderson. The Indians should be in aggressive contending mode right now, but ownership's unwillingness to spend pretty much cost the team a playoff spot last season. Unfortunately, nothing seems likely to change. Don't really pay any mind to those free agent losses. The bigger issue is the Indians' seeming eagerness to trade franchise shortstop Francisco Lindor. Winning should be the point, but in Cleveland that's clearly not the case.
Total free-agent WAR: 2.7. Positive WAR free agents: Marcell Ozuna, Luke Gregerson. Gregerson is an afterthought, but Ozuna hit 29 home runs in 130 games for a team that didn't have power to spare. He might be back, as the Cards made him a qualifying offer, but the crowded outfield situation may mean they don't make Ozuna a serious long-term offer.
Total free-agent WAR: 2.5. Positive WAR free agents: Kole Calhoun. Calhoun's a useful player and an Angels lifer, and the Angels are still trying to build a competitive roster around Mike Trout. That said, they have other spending priorities (the rotation, namely), and Jo Adell leads an impressive crop of outfield prospects that's on the way to Anaheim.
Total free-agent WAR: 2.0. Positive WAR free agents: Ivan Nova. The Sox have big plans for the rotation, but they may not involve Nova, who led the AL in hits allowed. Jose Abreu was on this list, but he accepted the qualifying offer and will return to the south side of Chicago. At this point, though, it's left to question whether Abreu is productive enough by positional standards.
Total free-agent WAR: 2.0. Positive WAR free agents: Hunter Pence, Logan Forsythe. Maybe Pence returns after his renaissance season, but the Rangers don't seem especially motivated on that front. Either way, they don't profile as contenders next season.
Total free-agent WAR: 1.7. Positive WAR free agents: Starlin Castro, Neil Walker. The Marlins are making some noise about spending a bit of money this winter, as they've been linked to Nick Castellanos and Jose Abreu. Bringing back Castro or Walker, however, is likely not in the cards.
Total free-agent WAR: 1.6. Positive WAR free agents: Jose Iglesias. The Reds are doing their best to return to relevance, and the good news for them is that they don't stand to lose much from a 2019 roster that was probably better than the 75-87 record it produced. Iglesias figures to be replaced by the comparable Freddy Galvis, which is perfectly defensible on the Reds' part. They'll spend their money on upgrades in the outfield, very likely. Among teams with realistic designs on the playoffs, the Reds will be the least affected by free-agent losses.
Total free-agent WAR: 1.3. Positive WAR free agents: Alex Gordon. The Royals are mostly rebuilding while not properly committing to the process. Gordon is a beloved figure in KC and a franchise icon, but he's going into his age-36 season and really has no place on a team that's trying to develop young talent. That said, the Royals do things differently, and it wouldn't be a surprise at all to see Gordon return. Either way, it won't affect the standings very much.
Total free-agent WAR: 1.1. Positive WAR free agents: Jordy Mercer, Matt Moore. Nothing really to see here. The Tigers are a terrible team that's presently doing a middling job of adding young talent. As free agents go, Mercer and Moore are fairly inconsequential.
Total free agent WAR: 1.0. Positive WAR free agents: Robbie Erlin, Craig Stammen, Aaron Loup. It's hard to project the Padres as potential contenders given that they lost 92 games a season ago. Yes, there's a deeply impressive base of young talent, but projecting a 15 to 20 win improvement is a stretch. If they're especially active at the top of the free-agent market, that estimation could change. Whatever the case, losing or re-signing one reliever of note who turns 36 in March (Stammen) won't move the needle much in either direction.
Total free-agent WAR: 0.3. Positive WAR free agents: Justin Smoak, Clay Buchholz. The Jays have been linked to top-flight catcher Yasmani Grandal, so the question is whether they're going to spend money for the first time since Mark Shapiro took over. The question is not whether Smoak and Buchholz return.
Total free-agent WAR: 0.3. Positive WAR free agents: Francisco Liriano. The 36-year-old lefty was effective across 69 appearances last season, but that's not going to matter much given the rudderless state of the Pirates right now.
Total free-agent WAR: 0.1. Positive WAR free agents: Tommy Milone. It's the Mariners, it's Tommy Milone. Moving along.
Total free-agent WAR: 0.1. Positive WAR free agents: Chad Bettis. It's the Mariners, it's Tommy Milone. Moving along. Wait, actually it's the Rockies, and it's Chad Bettis. Point stands, though.
Total free-agent WAR: 0. Positive WAR free agents: None. Lol.

Thanks to the FanGraphs-Roster Resource collective for the data.