Kelly Johnson: Slugger

As part of a critical five-run rally in the bottom of the fifth inning of yesterday’s Phillies-Diamondbacks game, Arizona second baseman Kelly Johnson slugged his NL-leading seventh home run. That leaves him only one home run behind his 2009 total of 8, a career low and a likely factor in the Braves’ decision to non-tender Johnson at the end of the 2009 season.

There are a couple of tools readily available to us with which we can evaluate a player’s home run hitting ability. First, HR/FB%. Simply put, hitters with home run power will hit more of their fly balls out of the park – that’s why Emilio Bonifacio and David Eckstein are at the bottom of the leaderboard and Mark Reynolds and Ryan Howard are at the top.

In prior years, Johnson’s HR/FB ranged from 7.5% to 13.8%. In 2010, however, Johnson’s HR/FB is a staggering 36.8% – 10% higher than Reynolds’s 26.0% league-leading rate from last season. Even though this almost certainly represents some luck, it also suggests that Johnson is hitting the ball extraordinarily hard right now.

We can also look at the sheer distance of the home runs that are hit, thanks to the excellent resource HitTracker Online. Again, we see sluggers like Reynolds, Joey Votto, Howard, Nelson Cruz, and Carlos Pena near the top of the farthest home runs hit in 2009.

So far, Johnson’s seven 2010 homers have traveled an average of 411 feet, well above the league average of 398.8 and his personal average of 400.4 last season. His 431 foot blast off of Nelson Figueroa on Saturday was the longest of his career. The “True Distance” supplied by HitTracker adjusts for wind, altitude, and temperature, so the move from Atlanta to Arizona shouldn’t be affecting these numbers.

There’s no chance that Johnson keeps slugging at the rate that he is now, but projection systems have been predicting a breakout for a couple of years now. Johnson is really driving the ball at this point in the season, and the distance of his home runs this year suggest that his latent power may have increased. The addition of Johnson has made the Diamondbacks lineup one of the best in the National League so far, and he will surely be a key to any run the Diamondbacks make in 2010 or 2011.