What does it mean to be “underrated?” The label suggests public perception is not in line with actual value, which for whatever reason is obscured. The term gets tossed around often and recklessly, like many labels. But in the case of Brandon Belt, there is some merit in making the claim.

Since the start of the 2015 season, Belt ranks 11th in the majors in walk rate (13.6%). He’s tied with Carlos Correa and Edwin Encarnacion for 17th in wRC+ (135). Over the last three-plus seasons, Belt also ranks 16th in on-base percentage (.375).

Who has the lowest ground-ball rate since 2015 among qualified hitters? Brandon Belt.

A large reason for the lack of a Brandon Belt Appreciation Society is because of his home ballpark, which last season ranked last in the majors for left-handed home-run park factor.

Consider Belt’s three-year batted-ball profile overlaid on a league-average park like Tampa Bay’s Tropicana Field:

Belt has had many an extra-base hit devoured by the marine layer and Triples Alley in San Francisco. And Statcast ball-tracking doesn’t adjust for atmospheric conditions.

One of the worst things that ever happened to Belt’s counting numbers was his decision to sign an extension with the Giants. Now, Belt’s injury issues and some performance inconsistency have also suppressed the full appreciation of his skills. Belt missed significant time with concussions last season and in 2014. There are other perception issues as documented last summer by longtime Giants beat writer Henry Schulman:

I think way too much is made of the “slumpy shoulders” thing, but I have been told privately that some do get annoyed at times by Belt’s sulking, or just the appearance that he is. As an aside, I have sensed a change in Belt the last two seasons, a seriousness we had not seen. I’ve been told something I actually can relate to personally, that Belt got weary of being the butt of a lot of jokes and did not want to offer as much fodder.

But coming off a torrid week and start to the season, Belt might be ready to shed any notions that he is underappreciated this season as his entire game is coming together.

Belt leads NL position players in WAR (2.4) at the moment. (He’s sixth in baseball with the top-five WAR-accumulators all in the American League.) He’s slashing .313/.413/.594 with a 176 wRC+, also an NL best, and he’s hit 11 home runs and is on track to reach and surpass 20 home runs for the first time in his career. Belt’s inability to rack up traditional counting numbers has, in part, prevented him from earning the reputation of an offensive force like he deserves. But while Belt has always been good — 30% better than a league average performer for his career — he’s never been this good.

So what’s different?

Belt has always been a fly-ball hitter, but this season he’s produced a career-best 50% fly-ball rate along with a career-best line-drive rate of 29.5%. When we think about Belt, we don’t think about home runs, although that might be different in another home park. Rather, we think about him squaring up pitches and spraying line drives all around the field with a quick and compact swing. Belt ranks sixth in “barrels” per plate appearance, according to Baseball Savant.

Belt has positive linear weights against every pitch type — save for the knuckleball — for his career, and he’s not a liability against most pitch types again this season. But he’s particularly crushing four-seam fastballs.

Belt is hitting .377 against four-seamers with a .721 slugging mark against them. The only pitch he is hitting more effectively, though in a smaller sample, is the changeup (.400 average and 1.000 slugging).

And as two-seam fastballs go on the endangered list, Belt, like most batters, is seeing more four-seamers, although fewer fastballs in general. Belt has been better against the sinker for his career (.346 average, .527 slugging), but the percentage of sinkers thrown Belt’s way have declined for a fifth straight season, from 20.2% in 2014 to 12.5% this year. Belt was held to a .239 average and a .493 slugging mark against four-seamers last year. He hit .268 with a .469 slugging mark against four-seamers in 2016.

This year? Belt has expanded his hot zone against four-seamers. Consider his slugging per pitch against four-seam fastballs:

2012-2017:

2018:

As pitchers have gone up, Belt has gone up with them. The average fastball Belt has faced has increased from a plate height of 2.69 feet in 2017 to 2.76 this season.

He has still covered fastballs down-and-in, middle-in, and middle-away with his quick-twitch swing.

Belt has made significant adjustments before. In 2013, he changed his grip and added power, for instance. Perhaps Belt is adapting to this four-seam fastball environment. Perhaps that’s the salient reason why, now healthy, he’ll no longer be underrated.