While working at the NFL as a Next Gen Stats research analyst, one of the projects I worked on was to quantify the difficulty of certain kinds of throws. This was inspired by Anthony Richardson's early 2024 season pass that traveled over 60 air yards while he was moving backwards to his left. The goal was simply to quantify how often throws like that happened and how rare that specific throw was. In the process of investigating this I was able to develop a methodology for quantifying the Passer Angle and classify specific kinds of throws such as Fade throws.
Passer Angle: The angle between the direction of quarterback movement to the location of the receiver at pass arrival. If you are moving in the same direction as the throw, the angle would be 0. If you are moving directly away from the receiver, the angle would be 180 degrees.
Fade Throws: A pass over 10 air yards with the quarterback moving backwards with sufficient speed (>= 1.5 yards per second).
These metrics were derived from tracking data and comparing against the tape to ensure that the cutoffs and frames of reference chosen were appropriate. I found that Fade throws are definitely a stylistic thing and different quarterbacks utilize them in different circumstances. Players like Jordan Love and Matthew Stafford use them all the time, while players like Bryce Young and Josh Allen only utilize them under pressure as another way of getting the pass out.
Additionally, I found that the iteration of the NGS expected completion probability model was not properly accounting for the added difficulty of these passes and therefore overestimating the likelihood of completion. Adding Passer Angle and Fade throws into the next iteration of the expected completion probability model will help the effectiveness and accuracy moving forward. Given the impact and reach of NGS, I was very pleased to have been able to find a logic-based approach that was able to aid the model that substantially.