It is simple to breakdown why Bryce Harper won the NL ROY award. He had the best season of any NL rookie. His 4.9 WAR was marginally higher than the 4.8 accumulated by pitcher Wade Miley, but in the end Harper was the everyday player and had a chance to make an impact on a baseball game everyday. That doesn't even factor age into the equation. The feats Harper accomplished at 19 are ones not likely to see duplicated in a generation.
Harper hit more homers than any 19 year old save Tony Conigliaro who was 19 in 1964. He had a higher SLG than any 19 year old save Mel Ott and Tony Conigliaro, and Ott was 19 in 1928. Bryce Harper finished with more total bases than anyone, more runs than anyone but George Lewis (1890) and Buddy Lewis (1936), and Harper finished with more stolen bases than anyone but George Davis and Ty Cobb (1906). Harper is tops in so many different categories it only helps to illustrate how versatile a player he is.
Look at the dates of those other great 19 year olds. At the current rate the next great one will come along sometime in 2067. The scary thought about Harper isn't what he did this season. It what he is going to do in future seasons. At the age of 20 Mel Ott's OPS jumped from the already good .981 to 1.084, Mickey Mantle went from an OPS of .792 to .924, and Ty Cobb went from .749 to .848. Harper was good this season and could be great as soon as next season. Just look at the AL ROY, Mike Trout. As a 19 year old he could only manage an OPS of .672, but as a 20 year old it jumped all the way to .963.
I am certain there are medical reasons for why there aren't many 19 year olds able to play major league baseball at the highest level and just as many reasons as to why the year between age 19 and age 20 seemingly makes such a difference. Think about Harper at 19 though. He roamed centerfield like an apex predator waiting to take down its prey and amassed 9.9 UZR. That isn't just a good UZR. That is elite.
Harper's homeruns weren't little either. He hit one to dead center at Fenway Park, one off the Blackberry sign in The Rogers Centre, and he hit numerous homers into Adam Dunn territory at Nationals Park. If Harper has a similar jump that these other great 19 year olds had between 19 and 20 then he very well could do as some have already predicted and win the NL MVP in 2013. If the kid is hitting balls into Adam Dunn territory at 19 imagine where they will go with just a little more power, and beyond that imagine how many harmless outs caught on the warning track will turn into homers.
When Bryce Harper hit a baseball it traveled with a speed and velocity rarely seen, but it was what Harper did after he hit a baseball that surprised everyone. Harper was expected to be a power hitter. He was expected to have the SLG, the homers, and the bat speed. What wasn't expected was his speed and aggressiveness on the bases. Harper never hesitated to take the extra base when it was offered. Even if it was barely an offer. There were numerous times his body would arrive to the base at the exact moment the ball was as well, but Harper would manage to get in ahead of the tag. Harper made the defense earn their out.
What Harper did in 2012 was worthy of the NL ROY award. What he does in the future, and perhaps as soon as next seen will be worth many other awards. In 2012 Nationals fans got to witness history, but it is only the beginning of what is projected to be a historic career.