The Polo Grounds, where the Giants played from 1911 to 1957, was a horseshoe-shaped stadium, which caused the fences to pinch the first base line. As a consequence of this, New York Giant first basemen often played 20 or 30 feet behind first base when the bases were empty, and well off the foul line, a long way from first base. There was relatively little foul ground that they could reach anyway, and a hard-hit ground ball that in another park would skip over first base and into the corner would often hit the wall just past first base and make a left turn, heading to center field. The first baseman, by playing deep and off the line, could sometimes pick up a ball that would be a double in any other park, and turn it into a ground out. That’s one reason the Polo Grounds, although it was a great home run park, was not a good hitter’s park overall, for most hitters.
New York Giant first basemen almost always had very high assist totals, because they were often playing a long way from first base, forcing the pitcher or occasionally the second baseman to cover first on anything other than a ground ball right at first base. Everybody who played there — George Kelly, Bill Terry, Johnny Mize, Whitey Lockman, even Zeke Bonura — always had a high assist total. Often, they led the league in first base assists:
Fred Merkle – 1911 (117)
George Kelly – 1920 (103), 1921 (115), 1922 (103)
Bill Terry – 1927 (105), 1930 (128), 1931 (105), 1932 (137), 1935 (99)
Johnny Mize – 1947 (118), 1948 (111)
Bill White – 1956 (111)
Johnny Mize, playing in St. Louis before the World War II, never had a hundred assists in a season, and never led the league in assists. Yet playing in the Polo Grounds in 1947-48, he had 118 and then 111 assists, leading the league both years.
Our thinking about defense is so primitive that we have little ability to deal with park effects for fielders. There are probably many such effects. Artificial turf probably reduces assists for infielders. A large foul territory certainly increases putouts for third basemen. Whoever plays left field for the Red Sox will probably have a low putout total, just because there isn’t much ground there for them to cover. Because the study of fielding has not progresses apace with the evolution of that of hitting and pitching, we have done little to document these effects.