MLB regions?

This is a newly discovered map showing the supposed range each MLB team's fan base has. A wonderful blend of great map design, intriguing topics, and legendary rivalries. We often think of boundaries only in the political context, but what happens when we think about sports? I am super curious to see what this map would look like with other sports leagues, both here in the US and elsewhere. What would the NFL look like? What about the English Premier League? What about the premier league on a global scale? I hope the creator of this map makes more.