Plenty of ink (does that metaphor still work?) has been spilled this season over Eric Hosmer's struggles, and rightfully so. As bad as Hosmer's season has been, the season Mike Moustakas has had this year actually leaves me more worried about his future than Hosmer's.
At a glance, this concern is laughable. Hosmer has accumulated -.4 fWAR this season, while Moustakas's fWAR is 3.6. In spite of the difference in Wins Above Replacement, I am more concerned about Moustakas's approach at the plate than Hosmer's which I worry will hurt his value more in the future.
Most of Moose's value this season is due to the incredible defense UZR credits him with playing. His UZR is 16.6, which is the best Ultimate Zone Rating of all qualified third baseman in baseball. To his credit Moustakas has played noticeably better defense this season than last season and his defense has been much better than advertised. I don't feel comfortable, however, projecting him as the best fielding third baseman in baseball. One just needs to look at Alcides Escobar UZR numbers to see rapid swings in UZR can happen, and that it takes at least three seasons to get a good feel about how strong a defender someone is.
Moose's offensive numbers, on the other hand, have not been very good and his peripherals are trending in the wrong direction. After 932 career plate appearances, Moustakas sports a .253/.303/.402 triple slash. As on offensive player, that puts him at ten percent below average compared to the rest of the league. If Moustakas had not crushed the cover off of the ball in April, more people might have noticed the lack of production at the plate from him.
This season, Moose has a .247/.299/.426 triple slash, which is slightly better than his .263/.309/.367 line last season because of the jump in slugging. Moustakas's plate discipline numbers, however, have taken a step back this season. His 6% BB% is exactly the same as last season, which was below league average both years. His strikeout numbers have actually increased this season, from 14.0% last season to 19.8% this season. Moose used to have an above-average strikeout rate, but has reverted to an average one this season.
His Pitch F/X numbers are also discouraging. Moustakas is swinging at more pitches outside the strike zone than last season, when he already swung at more pitches outside the strike zone than the average player. He is also making less contact overall, dropping from an above average 85.5% contact percentage to a below average 78.4%. The third baseman's swinging strike percentage has also jumped, from a better than league average 7.1% to a worse than league average 10.4%.
His hitting numbers are not all doom and gloom. His .ISO has jumped 74 points this season, and his BABIP is a little low this season at .277. Still, it's not good when a hitter is striking out more, swinging at more pitches outside the strike zone, and making less contact.
It's certainly possible I'm an overly worried Royals fan questioning a player who has 3.6 fWAR. Moustakas has certainly had a good season, even if I'm not entirely convinced it's been as good as fWAR is giving him credit for. Moving forward, I would feel much more comfortable about his future if his hitting statistics and plate discipline numbers improved and started providing some of his value.