Or, as many have pointed out, injuries happened in 2012 and 2014! The team was fine! Don't worry!
At this point you are probably thinking "Jesus, Rizzo. Can you please plan for this with some depth? It's the 4th year in a row it's happened!" but after that you are probably thinking "So which of these years is 2015 going to be most like? Will injuries make it a mess like 2013 or will they be a barely noticeable bump in the road like 2012 and 2014?"
First let's get a feel for the games lost to the starting offense in those other years. Ideally you'd get what? 130 games from the catcher and 154 games from everyone else? That would be 1208 games. How'd does that compare to what the Nats actually got the past 3 seasons?
2012: Ramos+LaRoche+Espy+Ian+Zimm+Morse+Werth+Bryce : 936 games
2013: Ramos+LaRoche+Rendon+Ian+Zimm+Span+Werth+Bryce : 1033 games
2014: Ramos+LaRoche+Rendon+Ian+Zimm+Span+Werth+Bryce : 1043 games
Not all the missed time was due to injury but you get the point. Missed some games the last couple years, more in 2012.
What would be our guess for 2015? Right now I'd pencil Span in for 40 missed games and Werth and Rendon for 10 a piece. Based on that pace, my guess is 2015 should be more like 2012 than the last two. It's still not impossible to have a relatively healthy year but it would pretty much require a nearly perfectly healthy rest of the season. A lot of games missed early is not a good start.
Now that we have an idea of what type of injury time lost to expect, how did these offenses do?
2012 : Ramos (almost all), Morse (2mo), and Werth (1/2 season) missed significant time, while Bryce spent a month in the minors. However across the board everyone hit, including these guys when healthy. LaRoche and Werth bounced back from bad 2011s, Desmond broke out, only Espy dipped below average. They ended up 5th in runs scored.
2013 : Ramos (1/2 season), Bryce (40 games), and Werth (25 games) missed time. Rendon took two months to get to the majors. Werth and Bryce hit better but Espy was terrible, LaRoche and Desmond took steps back, Span and Rendon were below average. They only dropped a spot to 6th in the NL but were roughly as close to 5th as 10th.
2014 : Ramos (almost half), Bryce (60 games), and Zimm (90 games) missed time. Ramos, Byrce, Werth, and Desmond all stepped back while Span, Rendon and LaRoche all stepped up. Finished 3rd in the NL in runs as close to 6th as to 2nd.
Those rankings matter because while the finishes are relatively close; 5th, 6th, and 3rd, the circumstances were completely different. The 5th in 2012 was about right - good, close to very good, but not great. The 6th in 2013 was illusionary. They were basically an average team who happened to pop out on the top end of that list. This is important because some people still like to float out "They were 6th!" Context, people. Context. The 3rd place finish last year was a bit of a mirage too. It sounds like an elite status but they weren't really close to the top. Still they were very good, about peak of what I would expect.
The Nats offense is generally good, can be very good, but has not been great. It hasn't really challenged for best in the league and it's dipped to around average. It's not a problem, but I can't all it a strength, either. It's part of the success but the smaller part.
Reading through this though you might see that the general feel of the offense remained roughly the same. Guys went up, guys went down. If the starters generally played about the same as a whole why don't the rankings follow the missed time? Glad you asked.
2012 : Miracle year where Lombo, Tracy, Moore, Bernadina, Suzuki, Ankiel were all at least not terrible and somewhat good. Despite the missed time this held the Nats offense up.
2013 : In a quick return to form everyone was universally terrible. The missed games cut deeper.
2014 : Mostly closer to 2013 than 2012 with a couple minor exceptions. Those exceptions helped not pull the team down like an anchor
But wait! I said 2014 was a peak and yet the bench wasn't great. Sure there were slightly fewer injuries than in 2012 but is there something else here? Yes, yes there is and it has to do with batting order.
The four best bats on the 2014 Nats were Span, Rendon, Werth and LaRoche. They also did not miss significant time. They batted 1st, 2nd, 3rd and 4th in the order, the slots that get the most at bats during a season. Contrast that with those positions in 2013. Span was still first and was below average, Rendon got a lot of time in the 2 spot and was below average. Lombo and Bernie, who were awful accounted for another 31 games there - that's almost 20% of the season. No one batted more often in clean-up than the off-bat of LaRoche.
What does this all mean for the offense in 2015? Well, given Span and Rendon are the biggest injury concerns and Matt Williams seems to love to plug their replacement in their batting slots, this does not bode well for 2015. Maybe I'd feel better if the bench was stronger but it's not. It's not that this means the offense is going to be terrible or anything. I would just expect a year closer to 2013's average output than 2012/2014's good to very good. Before you panic and scream "2013!" please remember the team won 86 games that year with that average offense.
How did they do that? Let's quickly check the flipside.
2012 : Great!
2013 : Steps back accross the board. Detwiler hurt, Haren bad. Still good, close to very good, but no longer team-carrying.
2014 : Great!
2012 : Braves were a legit threat. No one else was
2013 : Ditto
2014 : Braves collapsed. No one stepped up
And here you see the path to victory. Great starting pitching carried the team to a division title against stiff competition in 2012. Sure the offense might slip a bit from that year but the competition isn't there either.
Of course there is always...
2012 : Very good!
2013 : Eh.
2014 : Great! (really - check it out)
Here is a place the Nats could stumble. Storen hasn't pitched much. Soriano and Clippard are gone. Janssen appears to be no good. Blevins was cast off. It could be like 2013. Honestly, it could be worse. Relief is hard to pin down but a betting man says it's not going to be very good in 2015.
The short of all the above is that 2013 really was a perfect storm in a way. Well storm is too big a word. The perfect annoying drizzle. Not only did the offense kind of bottom out in expectations, but the starting pitching dipped, the relief pitching was mediocre, and the competition was there. In 2015 we don't expect a pitching dip or stiff competition. So even if worst case the offense does fall to mediocre, that pitching staff and the lack of a true threat should keep the Nats at 90+ wins and a decently easy ride to a division title. That starting pitching staff shelters you from a lot of problems.
Now could it be different than we think? Yes. If the bullpen falls apart AND if the Marlins (or Mets, I guess) are really good AND if the offense is affected a lot by these injuries then yes the Nats may have to fight to make the playoffs. But right now I'm still not worried. Wake me when Rendon is ruled out for the year and Max needs Tommy John.