Crushing fastballs led to Nolan Arenado's 2015 power surge

The Colorado Rockies are one of the more overlooked teams in the league. Last season they finished a poor 68-94, 24 games behind the division-winning Dodgers. In conjunction with a reputation for poor pitching, Rockies hitters were lousy last season as well. Colorado hitters finished with an anemic 9.6 fWAR, 4.5 of which came from their third baseman, Nolan Arenado.

Arenado had a breakout 2015 in which he smashed 42 home runs and put up a .287/.323/.575 slash line. All season he feasted on fastballs; in 213 plate appearances ending on a fastball, he hit 18 of his 42 home runs and put up a .346 isolated slugging percentage in 157 games. His durability and power took a major step forward last season, as he played in the most games of his career and destroyed fastballs throughout the season.

Fastballs thrown in the middle of the plate, either up or down, were simply demolished by Arenado; he even excelled at pitches out of the strike zone that were a bit high or a bit low yet still in the center of the zone. Interestingly, the top corners of the strike zone were blind spots, and all told the top corners of the strike zone yielded an ISO of exactly zero.

In 2015, Arenado benefited from a career-high home run per flyball rate of 18.5 percent. He also benefited from a career-best hard-hit rate of 35.8 percent, likely part of the reason Steamer projects a significant decrease in power. The system expects only 29 home runs and a slugging percentage of .516, down 12 percent from last season's .575, but his batting profile and maturation as a hitter make him a favorable candidate to be a league leader again.

Arenado demonstrated great success against fastballs, and although he is quite aggressive at the plate against all pitches, he managed a league-average whiff rate of 7.35 percent against the hard stuff. Arenado's achilles' heel remains the offspeed pitches, where he showed similar aggressiveness but paid dearly by not generating contact 17.5 percent of the time.

Arenado's plate discipline is unlikely to change, and he rarely gets on base via walks (he has a career 5 percent BB rate). He still manages to hit for average and power however, and it is the power surge that distinguished Arenado from the rest of the league and was the major cause in him taking a step forward as one of the best third baseman in the game.

It seems as if the Steamer projections will need to see more proof of the power surge before projecting him as an annual 35 to 40 home run threat. There are many reasons to consider Arenado as fully capable of similar power as 2015. His aggressiveness at the plate and ability to make solid contact against the hard stuff put him in a fortuitous spot to top the league in home runs again (Arenado tied with Bryce Harper to lead the NL in home runs). Arenado will do well to swing early and often as not to fall behind pitchers who will know that if they get ahead of him in the count, he's highly likely to swing and miss at offspeed junk pitches.

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Steven Martano is an Editor at Beyond the Box Score and a Contributing Prospect Writer for the Colorado Rockies at Purple Row. You can follow him on Twitter at @SMartano.