How Valuable Is Eric Hosmer?

Eric Hosmer's pending free agency seems both well and poorly timed.

The Kansas City Royals slugger is fortunate to be hitting the open market after a career year, but probably would have been more highly valued if this happened in a different decade.

Since making his big league debut in 2011, Hosmer is 10th among first basemen in RBIs (528) and his .282 batting average is ninth at his position. At a different time in baseball history, this would have mattered to teams.

Unfortunately for Hosmer, major league front offices are now a bit more nuanced. While the shiny RBI totals and average may have attracted general managers of yesteryear (and perhaps Ruben Amaro), those of today will presumably be less impressed by his 109 wRC+ and 7.7 fWAR (which rank 29th and 20th among the 60 qualified first basemen since 2011).

His average is somewhat empty, given it is only accompanied by an 8.0% walk rate and .153 ISO, which are both below what a typical first baseman delivers. His .339 on-base percentage is 20th among first basemen since 2011, while his .435 slugging percentage is tied for 36th.

Then there is his defense, which is probably in the range of bad (he is minus-13 in terms of DRS) and awful (he is nearly minus-28 in UZR). He has won three Gold Gloves, but while defensive metrics do have considerable error bars, it seems unlikely they've missed the mark here so much that one of the lowest-rated first basemen is actually among the best.

That said, Hosmer has been very good so far in 2017, especially over the past three months, and has already cleared the 2-win threshold in all three main iterations of WAR (his average career fWAR per 600 plate appearances is 1.1).

The idea of him getting some kind of mega-deal (the Royals reportedly expect Hosmer will ask for a 10-year contract) still seems like a tough sell, but he has made some adjustments that could increase his future value.

Post-April Surge

Hosmer's walk year could not have gotten off to a worse start, as he posted a 52 wRC+ in April, slashing .225/.281/.292. Since then, he has been 51% better than average and has a .345/.400/.550 line.

Some of this is due to a massive BABIP spike, even though Hosmer has run above-average BABIPs in all but one of his big league campaigns (his career mark is .315). Just as his .257 BABIP in April was unsustainably low, his .379 mark since is almost certainly unsustainably high. It is out of line with his Statcast data, as his xBABIP since May is .332, according to Baseball Savant.

This is still an above-average mark and is not too far from his career norms. It is also a skill that compliments his career 16.3% strikeout rate well.

The bigger question is whether Hosmer can sustain his recent power spike, as an inability to hit for much power has capped his offensive value for much of his career. He only has one season with an ISO that was more than 12 points better than league average, while this season, big league first basemen are posting an ISO that is almost 50 points higher than the overall average of .171.

Hosmer is at .177 this season, but since May, his ISO is .205 -- it is still lower than most players at his position but if this breakout is legitimate, a large Hosmer contract would be a lot more digestible.

There are reasons for optimism here, mainly the fact that Hosmer is hitting the ball to the opposite field at the highest rate of his career. Throughout his career, his production at the plate has very neatly tracked his oppo-rates, as you can see in this chart from FanGraphs:

Since arriving in the majors, Hosmer has been great when going the other way (191 wRC+) and bad when pulling the ball (84 wRC+). As Mike Petriello of MLB.com noted in July, during Hosmer's April slump, he had his highest pull rate since his rookie season (37%). After April 30, Hosmer has pulled the ball just 26.9% of the time (this would mark a career low) and is going to the opposite field on nearly 35% of his balls in play (which would be a career high).

Also, when Hosmer pulls the ball, it tends to lead to the ground balls which have been the biggest impediment to his power production. On pulled contact, Hosmer has a career 72.4% groundball rate (the fifth highest rate in the major since his debut) and a .176 ISO, which ranks 162nd out of 170 hitters since 2011.

His groundball rate when he goes the other way is still comparatively high (tied for 19th in MLB) but it still just 30.3%. Also, his .226 ISO on such contact ranks 23rd. We would expect Hosmer to rate highly in an area where he mostly hits the ball in the air, as he is in the 87th percentile in terms of exit velocity on non-grounders in the Statcast era.

In light of how he has prioritized the opposite field over the past three months, Hosmer's recent surge does indeed seem less like a fluke. This is not to suggest he will continue to post a 150 wRC+ going forward, of course.

His BABIP will presumably regress, as mentioned, and he is ultimately still hitting too many balls on the ground (thanks in part to a ghastly 81.9% grounder rate when he pulls the ball; his overall rate for the season is 54.1% and is at 52.2% since May).

Still, there seems to be a tangible improvement here and the rest-of-season projections appear to have taken notice.

It is worth noting that before the season, ZiPS projected Hosmer to post a .768 OPS, while Steamer had him at .799, so his strong season has actually moved the needle.

He will not get paid like he would have if teams still valued RBIs or batting average, but an average annual value in the ballpark of $16 million now seems possible.