The Harper and Zimmerman Effect
The Nationals are currently sitting at 34-34, something that seemed unfathomable at the beginning of what seemed to be a promising season. Much has been written about what some perceive the Nationals problems to be: errors, Danny Espinosa, Zach Duke and offensive ineptitude to name a few. Something that has been mentioned, but not truly quantified or comprehended, is how much the time missed by Ryan Zimmerman and Bryce Harper due to injuries has affected their fortunes this season.
The Nationals' longest losing streak this season is four games. They have accomplished this twice. The first time after Zimmerman went on the DL, the second time after Harper injured himself in Los Angeles. The Nationals longest winning streak is five games. This occurred the day after Zimmerman returned from the DL, one of the few times both were in the lineup together this year. Just from a general perspective we can already see what these two mean to the team.
Let's take a closer look now. The Nationals are 9-15 without Harper in the lineup; they are 6-9 without Zimmerman. From April 1 to April 17 and May 3 to June 1, the only times both Zimmerman and Harper were healthy together, the Nationals are 20-12, good for a .625 winning percentage. A .625 winning percentage stretched out over the 68 games the Nats have played so far would be worth 42.5 wins. For fairness' sake let's round that down to 42 wins or a record of 42-26, which would be one and a half games ahead of the Atlanta Braves for first in the NL East. That's a startling difference from where they are now.
Of course mathematically speaking, just stretching their winning percentage with both healthy out like that isn't the best practice. Too much goes into a baseball game to just say that the small sample of them together can be so easily applied to the rest of the year. Luckily there is a statistic that can directly measure a player's contributions to winning; you may now it as WAR. Also for future reference when I refer to WAR I mean the vastly superior Fangraphs version.
Let's look at Zimmerman and third base first. Zimmerman hasn't been his usual self on defense, so his WAR is a bit lower than his offensive production would suggest at .6 wins above replacement. Still that is more production than his replacements were able to give. Chad Tracy has been worth -.6 wins above replacement and while Anthony Rendon has been worth .7 WAR, a large amount of that value has come from his time at second base. From this we can see that Zimmerman has been worth between half a win to a whole win more than his replacements to the Nats and I would tend to err closer to the full win.
The difference between Harper and his replacements is where the Nats are really having trouble though. Bryce Harper has been worth 1.7 wins above replacement this season -- the Nationals second best player behind Ian Desmond -- despite missing a huge chunk of time.
Of Harper's five replacements in left field, only one, Roger Bernadina, has even performed above replacement level at .2 WAR. Jeff Kobernus, in his short time in the Majors, has been exactly at replacement level. The other three: Eury Perez, Steve Lombardozzi and Tyler Moore are at -.1, -.8 and -1.3 WAR respectively. Altogether the replacements have been worth -2.0 WAR, even more than Harper has been worth positively. That's a four win difference.
Put it together and Harper and Zimmerman being healthy would give the Nats around five more wins over their replacements. Those five wins would put the Nats dead even with the division leading Braves. While every team has injuries, the ones the Nationals have had could not have happened to more important players. Getting Harper back will be huge for the Nats and the numbers suggest that if Harper and Zimmerman are playing at full strength, the Nats could still have a run in them.