Master Melvin, Home & Away

Speaking of the Baseball-Reference.com splits, one of the more interesting cases is Mel Ott. As is well-known, Ott has the biggest home-field advantage in the 500 home run club, having hit 323 of his career homers at home, just 188 on the road; the short porches in the Polo Grounds, especially in right field, were an inviting enough target to help convert the diminutive (5’9″, 170-lb) Ott into the only man in the first 88 years of National League history to crack the 500 home run barrier (at his retirement, Ott was the NL home run king by a margin of 211 homers over Chuck Klein). But as Bill James has pointed out, while the Polo Grounds was a great home run park, it was actually not a hitter’s park at all, so Ott’s accomplishments aren’t to be devalued by virtue of the park.
We now have the data to back that up, at least for 1926-39, covering Ott from age 17-30, including the bulk of his prime (Ott hit 30 homers in a season only once after age 30). Ott in those years hit 211 homers at the Polo Grounds, 158 on the road (this does mean the split got wider as he aged – 112 more homers at home to 30* on the road). But he batted .297/.418/.553 at home, compared to .331/.421/.563 on the road, thanks in good part to hitting nearly twice as many doubles in the more normal-shaped parks around the league (235 to 124). The extreme example is 1930-31, when Ott hit 41 homers and drew 108 walks at home, compared to 13 homers and 77 walks on the road; yet, his overall line was .297/.419/.588 with 116 Runs and 121 RBI at the Polo Grounds, .345/.422/.537 with 110 Runs and 113 RBI on the road – nearly the same player in terms of value, but a completely differently-shaped batting line.
Let me illustrate this with a chart showing Ott’s percentages, batting average on balls in play, and doubles, triples, homers, walks, strikeouts, runs and RBI per 600 at bats at the Polo Grounds and in each of the other NL parks (I’m leaving out here Shibe Park, where the Phillies moved in 1938, presumably one of the causes for Ott’s homers drying up on the road after age 30):

As you can see, Ott was scarcely a home run hitter at all in Boston and Cincinnati, whereas his ability to get hits on balls in play was severely constrained at home. And, like Chuck Klein and pretty much everybody else, he was a holy terror at the Baker Bowl.
Here, just for comparison purposes, is how Ott hit team-by-team against each opponent when batting at home. As you can see, some ‘park’ effects could be the pitching staffs – for example, the Reds’ control-oriented staff was less apt to walk Ott in either venue – while, say, Ott’s home runs against the Braves and Pirates were clearly held down only by their home parks, his ability to get hits on balls in play was the same against the Pirates wherever he played:

* – Which breaks down as 6 more homers at Wrigley, 6 at Ebbetts Field, 5 each at Braves Field and Crosley, and 4 each at Sportsman’s Park and Forbes Field; Ott never went deep in Shibe Park. Year-by year Home/road HR breakdowns – Ott’s playing time dropped to around 125 games a year after 1943, I’m not sure if as the Giants manager he was resting himself more on the road, but clearly from 1942 on, his power output was almost entirely at the Polo Grounds:
1940: 12 home-7 road
1941: 19-8
1942: 23-7
1943: 18-0
1944: 21-5
1945: 18-3
1946: 1-0