Reason for optimism: There are easy areas of improvement that are rarely available to a team coming off a 95-win season.
Reason for pessimism: The Nationals squandered Stephen Strasburg's dominance in 2012, Bryce Harper's career year in 2015, Daniel Murphy's in 2016 and two years (so far) of Max Scherzer's brilliance.
In the field of asset management, particularly when it comes to investing in bonds, there's a portfolio construction concept known as a "barbell approach." Let's say an insurance company has a series of payments to make in seven years. It could construct its portfolio to have bond investments with an average duration of seven years by committing half its assets to short-dated investments (such as one- or two-year Treasury Notes) and the other half to bonds maturing more than a decade from now. The portfolio would achieve its goal but be heavy on both ends of the spectrum with little in the middle, hence the description "barbell approach."
The Nationals might not have the faintest idea about portfolio theory, but their roster last year had a decided barbell feel to it by season's end. Washington finished 2016 with no fewer than five position players posting at least 3.0 WAR. That's almost always the mark of a very good team, and sure enough, only the Red Sox and Cubs matched the Nationals with five such players. While keeping that kind of company, you certainly wouldn't expect Washington to also be hobnobbing with the dregs of the league. Yet no other team had as many players post at least -1.0 WAR as Washington did. There were only 18 everyday players across all of Major League Baseball with at least -1.0 WAR, and the Nationals had three of them, matched only by the Rockies for individual ineptitude.
"Earning" -1.0 WAR is particularly damaging because it requires significant playing time, and the Nationals' three sub-replacement players, Ben Revere, Clint Robinson, and Ryan Zimmerman, burned 1,067 plate appearances while posting -3.7 WAR as a trio. In perhaps the single largest upgrade across the majors this offseason, Revere has been replaced by Adam Eaton, who was acquired in a costly trade with the White Sox, but it was a deal I heartily endorse because it represents an enormous improvement to the lineup and defense. As the Nationals were a 95-win team in both form and substance last season, that upgrade alone is enough to make them a baseline 100-plus-win team before other marginal changes.
From that lofty level, there are a number of haircuts to take to the projection. Late free-agent signing Matt Wieters will attempt to match the .307/.354/.496 production Wilson Ramos produced last year, a dubious task, given Wieters' career marks of .256/.318/.421 and the fact that he's on the wrong side of 30. Detracting further, according to Baseball Prospectus (for years on the cutting edge of quantifying catcher framing skills), is that Wieters appears to cost the squad a win a year just from lost strikes, compared to Ramos.
Then there's regression. Daniel Murphy, at age 31, had by far the greatest year of his career, and his defection alone from the Mets to the Nationals can be used to explain the reversal of fortunes from 2015 to 2016 for both teams. Jayson Werth is decaying before our eyes, and for some reason, the Nationals appear to have permanently cast Zimmermann in the role made famous on the I-95 theatre circuit by Ryan Howard, as a former face of the franchise now killing the team at first base. Despite those problems, the presence of Bryce Harper and Trea Turner along with Eaton means there's plenty of youthful upside to offset any dead weight the veterans supply.
One place you won't find dead weight is in the rotation, and it's the chief reason the Nationals are in the final stages of the "win now" era. Top to bottom, it's the best rotation in all of baseball, yet it still qualifies as top-heavy, an enviable combination built for regular season and postseason dominance. Backing them up in 2016 was merely a bullpen with an ERA of 3.37, second-best in the majors. There's a meaningful amount of turnover among the relievers, which is a great way to regress back toward a league-average ERA, but for what it's worth, many of the arms shed had ERAs above 4.00, including three high-usage relievers.
One of the hidden reasons the Nationals cruised to the NL East title last season was a huge increase in their defensive efficiency, which would have been hard to predict based on their performance the season before and the addition of Daniel Murphy, who typically looks less comfortable playing the field than a 60-year-old widow. Defensive efficiency will be a key metric to keep an eye on with the arrival of the well-regarded Eaton in center field.
I expect the Nationals to unseat the Cubs as the team that allows the fewest runs in the majors this season, and despite my reservations about Werth, Zimmermann and Wieters choking the offense, Washington has a reasonable path to a 100-win season. In fact, owing to that young but experienced talent and the brilliant rotation, to my eye, you're looking at the NL Pennant winners. Play the over.
2016 projection: 95-87 (first in the NL East)
Bet recommendation: Over