Eric Hosmer has a problem against left-handed pitchers

Eric Hosmer was the Royals first round pick and star of the franchise, at least with with his persona and media presence. He is known for his post-season heroics such as his triple against Oakland in the 2014 Wild Card Game, his home run against the Angels in the 2014 ALDS, his clutch hit against the Astros in the 2015 ALDS, and of course his dash home against the Mets in last year's World Series.He finally reached the 25 home run, 100 RBI plateau this year, causing some to crow about his performance. He has endeared himself to fans as one of the home-grown heroes of the Royals team. He is also known for his selflessness off the field, being nominated for the Roberto Clemente Award. Through and through he's a fan favorite.

I feel like I know Eric Hosmer pretty well when it comes to his baseball career. I could tell you that he had LASIK surgery, that he dated a local television anchor, he hit a home run in his first at-bat in AA, and his first home run was off of A.J. Burnett. What I didn't know until looking at Hosmer's career was this:

Player	wRC+
Steve Cox	55
Ryan Howard	85
Eric Hosmer	85
Justin Morneau	86
Carlos Pena	96

That's a list of the worst-hitting first basemen against left-handed pitchers since 2002 by Weighted Runs Created Plus (wRC+). Steve Cox washed out of the league quickly, so Hosmer is really tied for last among players with staying power. Now this is only among first baseman and most first basemen are lefties so it makes sense they would struggle a bit against their same handed counterparts. However, even against his peers, Hosmer finds himself near the bottom, equal to Ryan Howard, which in 2006 might have been something, but more recently has been absysmal.

When you widen the view to all positions it gets a bit more generous (min. 500 PA):

Rank	Player	PA	wRC+
10	Grady Sizemore	1377	84
11	Chone Figgins	1635	84
12	Pablo Sandoval	1118	85
13	Eric Hosmer	1229	85
14	Erick Aybar	1509	85

Hosmer moves up a bit but is still thirteenth-worst in baseball against lefties. Basically, when facing lefties, Eric Hosmer becomes Andrelton Simmons.

Let me show you one more thing:

Name	PA	ISO
Eric Hosmer	1229	.112
Freddie Freeman	1228	.152
Adrian Gonzalez	2367	.152
Justin Morneau	2041	.159
Carlos Santana	1328	.161

That's isolated power (a stat trying to isolate power from batting average) against left handers among active first basemen. Unlike wRC+ there is no jumble among the bottom. It's Eric Hosmer, a 40 point gulf, then Freeman and Gonzalez. A 40 point difference in ISO is the difference between Ian Kinsler and Scooter Gennett, Joe Randa and Carlos Febles, or Brandon Crawford and Nori Aoki.

Maybe this surprises you. It surprises me. I mean, Eric Hosmer was the guy who did this:

this:

and this too:

That's a count of three home runs off of Chris Sale, not just the best left handed pitcher in baseball but one the the best overall pitchers. Eric Hosmer has three home runs off of him. Three home runs off a particular pitcher isn't that big of a deal but three home runs in a career vs Chris Sale is impressive. There are only ten hitters with 3+ home runs against Sale for their careers...none of them are left handed batters. Even more impressive, Hosmer collected these blasts all in one season - this one! You would think a guy capable of doing that to Sale wouldn't struggle so much against every other lefty out there.

So what does Hosmer versus a left-hander do differently that Hosmer versus a right-hander?

Platoon	GB/FB	LD%	GB%	FB%	IFFB%	HR/FB	Pull%	Cent%	Oppo%	Soft%	Med%	Hard%
vs LHP	2.22	18.9%	55.9%	25.2%	8.6%	9.9%	33.5%	39.5%	27.0%	20.3%	49.8%	29.9%
vs All	1.93	19.6%	53.0%	27.4%	8.5%	13.3%	35.2%	36.4%	28.4%	19.0%	47.9%	33.1%
vs RHP	1.81	19.9%	51.5%	28.5%	8.5%	14.7%	36.1%	34.9%	29.0%	18.3%	47.0%	34.8%

Really it's just power. There aren't any huge deviations in his batted ball profile when it comes to facing different handedness necessarily. He's always been a groundball hitter and it's a bit more exaggerated versus lefties compared to righties. Really though it comes down to power. Hosmer makes a good bit less hard contact against lefties and the same for home runs per fly balls.

Left handed pitchers also pitch him differently:

Lefties work him away more and much lower in the zone and have double the slider usage (which is typical generally for same-handed match ups). His highest whiff% among any pitch thrown by either handed pitcher is highest against the left handed slider (32%) and also the lowest fly ball% (14%).

Hosmer though has no troubles against right-handed pitchers. He has a career 117 wRC+ (17% above league average) and .164 ISO (52 points above his LHP ISO). He doesn't dominate right-handers (for instance fellow left handed struggler Freddie Freeman has a 156 wRC+ vs righties) but it is by far his strongest side.

I'm not really advocating for Hosmer to be part of a platoon at first base. First, the Royals don't really have anybody to platoon him with except for perhaps Cheslor Cuthbert, who isn't exactly prodigious lefty masher. However it has become noticeable how bad Hosmer has been against left-handers. If an opposing team has the option, they should never run a right-handed reliever against him.