Looking at just the 2018 season, I cut the tree (red line) into four general groups and showed each group’s Thrownar (it’s like PassSonar, but for throw-ins, get it?). Each bar on the Thrownar represents the relative frequency of throw-ins taken at each 15-degree interval and the color is the average distance for each. So the most frequent angle will always be the longest bar and the rest are scaled to that.

Overall, teams break down into those that mostly take vertical throws-ins and those that will mix it up with some backwards and horizontal throws as well. Most teams are in the former category, but six courageous teams do something a bit different. In group one, Philadelphia, Columbus, and Orlando most commonly throw backwards from the left side of the field, and rarely throw vertically from the right. Group two (New York City, LAFC, and Kansas City) are similar to group one, as you’d expect from the tree, but are more balanced with their long vertical throws on either side and also have higher frequencies of lateral throw-ins. Again they throw backwards more from the left than from the right. I can’t think of a good reason why throw-ins are more likely to go backwards on the left side of the field than the right. Maybe it has something to do with most players being right footed? If you have any ideas please let me know.

On the other side of the tree, groups three and four represent the teams that predominantly throw vertically. Both show similar patterns, except group four takes 33% of their throws almost directly forward, whereas for group three it is 23%. Group four includes New York Red Bulls and New England, who apparently translate their typical direct passing style to throw-ins by very rarely going backwards.