Bryce Harper the Left Fielder
With the acquisition of Denard Span to play center field and bat leadoff, a new defensive home had to be found for Harper. In 2012 advanced stats didn't just rate Harper as a good defensive center fielder he was rated as a great one. The Span move makes the Nats better in two positions of weakness and it also allows Harper to move to a more offensive position and focus on that aspect of his game. Left field is the second least important defensive position according to the defensive matrix, and often times it is the home of some of the games best sluggers.
For a quick comparison the average MLB center fielder hit .265/.330/.418 in 2012 and the average left fielder .261/.327/.431. While left field is traditionally a more offensive position current left fielders only managed a .009 OPS advantage over their CF brethren in 2012. This doesn't nor should it change the perception of left field as the less important defensive position of the higher offensive position. All it means is that there aren't a lot of good left fielders right now. In WAR there are built-in bonuses for playing different positions, a good offensive player at an up the middle position will be rated higher than a good offensive player at a corner position, because an up the middle player that can hit is more valuable.
Harper in 2012 hit .270/.340/.477, above average as for both a center and left fielder. At around .800 OPS a good hitter is a good hitter no matter what defensive position they play, and Harper is in that class. As good a defensive center fielder as Harper was his range and speed should make him a better defender in left. That isn't always the case as it is a different read of the ball of the bat, but physical skills wise a good defensive center fielder is an even better defensive left fielder. Whatever positional difference bonus is lost in WAR by moving from center to left is going to be picked up immediately because Harper will be a better defensive left fielder. There is also the fact that Harper is going to be measured against his peers, and he may already be one of the top five left fielders in the game without having played a single inning.
In some order the projected top left fielders in baseball should be Alex Gordon, Matt Holliday, Justin Upton, Ryan Braun, and Bryce Harper. In 2012 the five best left fielders in baseball ranked by fWAR were Ryan Braun, Martin Prado, Alex Gordon, Matt Holliday, and Alfonso Soriano. If we were to rank the 2012 left fielders by offense alone then Harper's 2012 wOBA of .352 would have him tied with Jason Kubel for 8th best in all of baseball. Harper as a rookie and coming from a less offensive position is already in the top third offensively for the position, but again he is an above average enough hitter that his bat will play wherever the Nats choose to put him on the diamond.
As we saw earlier though when we compared the average offense for center to left the disparity isn't as much as one would expect when comparing a primarily defensive position to a primarily offensive position, and that is because there are more talented center fielders playing right now than left fielders. Look at the list of top left fielders from last season. There is one name that sticks out that no one would include in their list of top players. Now look at the top five center fielders by fWAR from 2012: Mike Trout, Andrew McCutchen, Michael Bourn, Austin Jackson, and Bryce Harper. Those are all quality major league players and in fact Harper, the fifth ranked left fielder, had a 4.9 fWAR compared to 4.0 for Soriano, the fifth ranked left fielder.
There are more talented center fielders playing the game of baseball right now than there are left fielders. Harper's wOBA ranked him only one place higher as a center fielder last season than it did as a left fielder and that is only because Matt Kemp doesn't qualify. If Kemp is added into the list then Harper is in the same place offensively as a center fielder as he is as a left fielder. This is not what one would assume to find when they look at a defensive position vs. an offensive position. If we move to the extremes and compare a catcher to a first baseman the average 2012 catcher hit .248/.318/.400 and the averaged first baseman .262/.336/.442. Moving just two spots down the defensive matrix from catcher to center fielder and just one up from first baseman to left fielder it wouldn't be expected that the gap would narrow that quickly.
These surprising results aside, Bryce Harper should hit better in 2013 than he did in 2012. Many fear the sophomore slump, but by now Harper has proven not to put expectations on him and with added muscle and private astronomical goals, the ceiling for Bryce Harper is MVP. The floor for Harper may very well be a repeat of his offense from 2012, but with more playing time that will lead to a higher fWAR value. Harper as a left fielder isn't going to be that much different than Harper as a center fielder, and with less defensive stress and strain on the body could be even better.