Having some of this Gretzky field sense myself, if I may say so, I think they are a bit off base in this article. At least in the examples given they don't apply to Gretzky's field sense whatsoever in my opinion. For the tennis and volleyball examples, one is training on being able to predict trajectory by watching directly and picking up on various clues. Also, with the Australian rules football example, I believe this is completely backwards as to how Gretzky and similar players in hockey process information.

From my own experience and the way I understand how Gretzky processes information, it basically comes from experience and the ability to track 3-4 other players (maybe more if you count the other team) simultaneously as to their predicted movement on the ice. This comes from being able to process what one would do if you were in their shoes without the need to look at them or focus on them. When I play with players that approach the game very very similarly to myself I have an extremely good idea exactly where they are going to be on the ice at any given time. I know what they are going to do if I cut one way or the other. I know what they are going to do if a defender moves a certain way. I don't need to glance at them or assess the field.