Solving Breaking Stuff Key to Breakout for Hosmer, Moustakas

With Wil Myers headed to Tampa as part of the gargantuan bounty paid for James Shields, Eric Hosmer and Mike Moustakas will be subject to even more scrutiny from Royals fans. Kansas City's cornerstone corner infielders, both former top ten prospects as rated by Baseball America, are coming off disappointing sophomore seasons. Hosmer didn't have many bounces go his way (his batting average on balls in play was just .255), but his slugging percentage dipped by over 100 points from 2011 (.465) to 2012 (.359). Moustakas, meanwhile, hit 20 homers but did so with a sub-.300 on-base percentage (.296).

For Hosmer and Moustakas to have breakout seasons, they'll first have to solve breaking stuff. Both struggled mightily against curveballs and sliders in 2012, with Hosmer posting the seventh-lowest slugging percentage (.233) among qualified hitters and Moustakas (.313) also doing far less damage than the league average (.357). Hosmer has to start lofting breaking stuff, while Moustakas has to stop lunging at it.

Check out Hosmer's ground ball rate by pitch location against breaking pitches, compared to the league average:

Hosmer's ground ball rate vs. curves and sliders

League average ground ball rate vs. curves and sliders

Hosmer hit a grounder about 57% of the time last year, way above the 47% major league average. Here are some of the players who hit grounders on breaking stuff about as often as Hosmer: Nyjer Morgan, Jose Tabata, Juan Pierre and Brian Bogusevic. Power hitters, those fellows are not.

While Hosmer hits too many choppers, Moustakas chases too many breaking pitches off the plate. Here's his swing rate by pitch location against curves and sliders, and then the league average:

Moustakas' swing rate vs. curves and sliders

League average swing rate vs. curves and sliders

Moustakas chased about 39% of breaking pitches thrown outside of the strike zone, compared to the 32% big league average. Perhaps recognizing his breaking ball giddiness, pitchers threw him a curve or slider over the plate just 41% of the time (46% MLB average).

Hosmer (entering his age-23 season) and Moustakas (24) both have youth on their side. But now that the Royals have decided that six years of potential superstar production from Myers is worth giving up for two years of Shields, K.C.'s corner infielders are under even more pressure to produce. Their performance against breaking stuff will be crucial during a make-or-break 2013 season.