After struggling through one of the worst seasons in baseball history last year, the White Sox's Adam Dunn is giving the Sox the sort of season his career promised. Even more so by one measure: his isolated power, or ISO, is the highest of his career so far this year, second only to Josh Hamilton.

Long regarded as one of the exemplars of the three true outcomes, he's taken that to another level, with career highs not only in ISO but in strikeout rate (37.1 percent, about a point and a half higher than last year) and walk rate (19.4 percent, about four and a half points higher than last year). About 64 percent of his plate appearances this year have ended in a walk, a strikeout, or a home run; he has two more home runs than singles so far, 17 to 15.

(Update: To put his singular approach to the plate in context, Dunn has the highest strikeout rate in baseball this season, the second-highest walk rate, and the second-highest isolated power.)

And when he hits a home run, he hits it really, really hard. ESPN's Home Run Tracker measures every home run hit in baseball by several criteria, including true distance (how far it would go uninterrupted), standard distance (how far it would go with no wind at 70 degrees at sea level), and speed off bat, the latter two being excellent measures of how hard a player is hitting the ball. I went through all major-league players with at least 10 home runs this year, and mathematically speaking Dunn is killing the ball.

* Standard Distance: Dunn's home runs have gone for an average of 411.7 feet. Only Mark Trumbo of the Angels, with ten home runs at an average of 420.8 feet, is averaging a longer distance.

* Speed Off Bat: Dunn's home runs come off his bat at an average speed of 106.7 miles per hour. Trumbo's home runs have averaged 107.8 mph; Dunn is behind Trumbo and Marlins teammates Giancarlo Stanton (107.6 mph) and Hanley Ramirez (106.9 mph).

* "No Doubt" Home Runs: Home runs that "cleared the fence by at least 20 vertical feet AND landed at least 50 feet past the fence. These are the really deep blasts." Dunn leads the major leagues with eight.

* "Just Enough" Home Runs: Home runs that "cleared the fence by less than 10 vertical feet, OR that it landed less than one fence height past the fence." Dunn has two; Josh Hamilton, who leads all of baseball with 21 home runs, has six. Edwin Encarnacion, tied with Dunn with 17 home runs, has seven "just enough" home runs; Curtis Granderson, also tied with Dunn, has three, plus two "lucky homers," i.e. ones that "would not have cleared the fence if it has been struck on a 70-degree, calm day."

So Dunn isn't just hitting home runs this year, he's hitting quality home runs. Home Run Tracker goes back to 2006; the only year in that period that Dunn's speed-off-bat fell below 104mph and his average standard distance fell below 400 feet was last year. The only years Dunn has averaged above 106mph and 410 feet are 2008 and 2012.

What's the difference? Dunn is crushing balls down the middle, particularly in the dead center of the strike zone, and especially fastballs. As Bill Petti points out at Fangraphs, he's not actually seeing more of these pitches, he's just swinging at them more often.

Dunn's hardest-hit home run this year, which came off the bat at 115.2 mph, was a low fastball hit last week off the Rays' great rookie lefthander Matt Moore, tying him with Albert Belle for 62nd all time at 381 home runs (he hit number 382 on Friday):

The most spectacular home run of 2012? Probably Giancarlo Stanton's off of Jamie Moyer on May 21st. 1) It left his bat at 122.4mph, the fastest in the past five years, according to Home Run Tracker 2) He hit the fastest home run ball in the past five years off Jamie Moyer, which means he really hit it hard 3) It was a grand slam 4) He wrecked the scoreboard. Stanton's going to be a fun player to watch going forward.

Photograph: Chicago Tribune