The 2015 Washington Nationals are like the body that washes up on shore that was shot, stabbed, bludgeoned, and set on fire before being thrown into the water and determining the exact cause of death is not going to be easy. Matt Williams will be the first to pay for the results of the 2015 Nationals but no manager has that great an impact. The Nationals expected record is five wins better than their current record and while some of those games can be attributed to Matt Williams' mismanagement a couple can be attributed to luck and at best Matt Williams cost the Nationals three games. Contrast this to the beleaguered and underwhelming bullpen that ranks 21st in the majors in WPA and blew several crucial saves in August and September. An average manager gives the Nats three more wins and an average bullpen five, and even then that isn't enough to be first in the division.
If the manager and bullpen were better it would still be a fight but neither alone is a cause of death. The death spiral of the Washington Nationals started on July 31. Starting that day the Washington Nationals were up three games in the division and nine games over .500. The Nats had just gotten Jayson Werth, Anthony Rendon, and Ryan Zimmerman back into the line-up and Denard Span was in the midst of a rehab assignment. The Nats were confident that a couple of these players could step back into the line-up and perform like themselves, but in order to do that the Nationals needed to sit the productive duo of Danny Espinosa and Clint Robinson.
As everyone is aware the Nats made no significant moves at the trade deadline, the one move they did make ended up not helping because Drew Storen imploded in his new role, and all the returning players struggled for the entire month of August or returned and got re-injured. Here we are presented with two other possible causes of death. The under performance of the returning injured and inactivity at the trade deadline to acquire any insurance. At the same time as this was happening the bullpen was already imploding, and it is tough to separate just how many games the Nats were cost by these two factors. They had some impact but not as much as either the bullpen or the manager and while the wounds were severe neither was enough on its own to be the cause of death.
When the 2015 Washington Nationals were constructed they were supposed to be able to weather the storm of injuries or poor bullpen performance because the starting pitching was supposed to be so great. While the starting pitching ranks seventh in the majors in fWAR and FIP they were promised to be much better. Not just the best for 2015 but possibly one of the greatest rotations of all time. If they had lived up to that billing none of the other factors would have mattered all that much as opponents would struggle to score in every game against the Nationals.
Instead the Nationals starting pitching let far too many opponents into the game, and it wasn't just that they performed below expectations it was how uneven the performance was. Look at Jordan Zimmerman, a pitcher known for consistency, and while his 3.68 ERA appears good he has allowed six or more runs five times in 2015. Then there's the case of Max Scherzer and Stephen Strasburg. Again the overall numbers are good but Shcerzer had a great first half and a pedestrian second half while Strasburg is the reverse with a few injuries thrown in.
The starting pitching was the life raft that was to carry the shot, stabbed, bludgeoned, and burning body of the Washington Nationals to some level of relative safety. It failed, but on its own was not the ultimate cause of death for the 2015 Washington Nationals. The line-up gets a lot of blame from a lot of people and there were players that greatly under performed on the offensive side of the ball (Ian Desmond) but the Nationals are still third in the NL in runs per game and even though most of that is Bryce Harper it is hard to fault the one part of the team that actually did it's job and performed to expectations.
The 2015 Washington Nationals are dead and many factors lead to their demise but no one had so great an impact that if the others hadn't have happened the season would still have ended prematurely. The Nationals may have been shot, stabbed, bludgeoned, set on fire, and thrown out to sea but the real cause of death was sudden cardiac arrest brought on by the shock and trauma of a variety of injuries.