The philosophy of hitting is changing right before our eyes.

Growing up, we were taught that hitting line drives up the middle was the best-case scenario from any particular plate appearance. But these days, power hitters like J.D. Martinez are challenging that conventional wisdom in favor of putting more balls in the air.

A number of players have benefited from the "fly-ball revolution," but a perfect case study is Seattle Mariners first baseman, Yonder Alonso. Through the first 2,343 plate appearances of his big league career, he collected just 39 home runs with a 45.3% ground-ball rate and 32.6% fly-ball rate. After making a conscious decision to change his approach this past offseason, some incredible results have followed -- Alonso has posted a 33.3% ground-ball rate and 44.7% fly-ball rate through 402 plate appearances this year, which has led to 23 homers.

Theoretically, hitting more fly balls provides a better chance of hitting more homers, but it doesn't always work that way. Some players who hit way too many ground balls have proven to be awfully resourceful with the balls they do put in the air.

The following eight hitters are all among the league leaders in ground-ball rate, yet they've already collected at least 20 homers this season.