Play: With two out in the top of the 9th of a game which St Louis led 2-1, Cubs batter Nico Hoerner hit a 1-1 curveball from Cardinals pitcher Alex Reyes on the ground toward third base. Cardinals third baseman Nolan Arenado picked up the baseball as it rolled along the foul line, believing he had retrieved the ball in foul territory.
Call: HP Umpire Phil Cuzzi, however, ruled the ball fair, deeming that Arenado touched the ball as it was on or over fair territory.
Rules Review: As is critical to objective analysis, we again begin with the relevant Official Baseball Rules, namely the definition of terms: "A FAIR BALL is a batted ball that...while on or over fair territory touches the person of an umpire or player" while "FAIR TERRITORY is that part of the playing field within, and including the first base and third base lines, from home base to the bottom of the playing field fence and perpendicularly upwards. All foul lines are in fair territory."
Analysis: Next up is a discussion of the orbital nature of a baseball: it is a sphere and, given the aforementioned definitions for fair ball and fair territory, a ball need not actually contact the ground in fair territory while being touched by a fielder in front of first or third base for it to be deemed fair ("on or over").
Sidebar: Had this been a first contact by the batted ball in the outfield, it would need to make contact with the left/right field foul line or within those lines to be deemed fair [a recent MLB Umpire Manual interpretation add-on regarding batted balls in the outfield clarifies this to be the case for outfield hits, but not for infield hits]).
Related Post: Ask UEFL - Judging a Fly Ball as Fair or Foul (Video) (7/13/18).
Accordingly, we have a parallax problem because this does not necessarily involve a ball touching painted line on the ground, but a portion of the ball breaking a plane nary inches off of the ground.
In our 2018 video regarding parallax in baseball and hockey, we simulated the difficulty in accurately assessing a ball (or puck)'s location when said object was not entirely flush with the ground and the camera angle provided was not positioned directly down the line used for fair/foul consideration.
The age-old question, then, of whether Cuzzi's call was correct or not may never be known: Cubs fans on Twitter think Cuzzi got it right, Cardinals fans think Cuzzi got it wrong, and neither side has definitive video proof to support their conjecture—especially with pitcher Reyes' leg blocking out the moment of truth on a key replay angle. In other words, this ruling truly is the "call stands" of fair/foul decisions.
(Note: The Cardinals won the game on a fly out several pitches later) | Video as follows: