Eaton was coming off a career year when the Nationals acquired him from the Chicago White Sox in December 2016. His 5.9 WAR were 12th-best among position players. The veteran outfielder was also signed to a pretty modest five-year, $23.5 million extension to his 2015 contract.
Washington included Lucas Giolito, who at the time was one of MLB's top prospects, in its trade package to Chicago, highlighting just how much value Eaton seemed to have in terms of on-field production and cost control.
The 31-year-old was on pace to be even better in his debut campaign with Washington, posting an .854 OPS through 23 games. Then he suffered a torn ACL, which presaged the years ahead. He was limited to 95 games in 2018, and his performance has steadily dipped since that injury.
Eaton finished 2020 with a .226/.285/.384 slash line along with four home runs and 17 RBI in 41 appearances. A fractured left index finger ended his season in September.
"For a 60-game season to settle my fate for next year is kind of crappy," he said, per NBC Sports Washington's Todd Dybas. "I try to be as consistent as I can for this team when I am on the field. It's unfortunate, but it's kind of how the year is going."
All signs pointed toward the Nats declining Eaton's option.
His days as an everyday center fielder ended when he tore his ACL, and he has struggled defensively in right field. If not an outright upgrade, Washington can at least find a replacement for less than what it will be paying Eaton.
Free-agent spending was trending downward before the COVID-19 pandemic put a serious strain on teams' finances.
The upper echelon of stars (George Springer, Trevor Bauer, J.T. Realmuto, Marcus Semien, etc.) on the market will probably still command top dollar. Mookie Betts signed his 12-year, $365 million extension in July when the implications of the pandemic were clear for everyone to see.
Players on Eaton's level will probably be squeezed the most because they're not so good as to be totally irreplaceable. Marcell Ozuna had 29 home runs and 89 RBI with a .472 slugging percentage—and two All-Star appearances to his name—heading into last offseason, and all he could manage was a one-year, $18 million deal from the Atlanta Braves.
Ozuna is available once again, and any one of Joc Pederson, Yasiel Puig or Michael Brantley would be a sensible target for Washington.
Assuming the Nats don't simply bring him back on a lower salary, Eaton's time in the nation's capital has drawn to a close, which will likely lead to retrospective analysis about the trade that got him there.
Giolito has turned into a top-of-the-rotation starter, while Dane Dunning is MLB.com's No. 98-ranked prospect and finished with a 3.97 ERA in 34 innings as a rookie.
The White Sox will continue to reap nice dividends from that deal. The Nationals, however, won a World Series in 2019 thanks in some part to Eaton's contributions. He slugged .560 with two home runs and six RBI against the Houston Astros in the Fall Classic.
That alone was enough to make the trade worth it for Washington.
Stats are courtesy of FanGraphs unless otherwise noted