The same idea as 3rd Down Splits, isolated to 4th down plays -- the highest-leverage down in football.
Inputs: Every play on file where down = 4 and this player was involved.
What is "garbage time"?
A 7-tier rule (bigger lead required as the clock runs down) that flags plays happening in a game that is no longer competitive -- e.g. a 30+ point lead right after halftime, or a 12+ point lead inside the final 3 minutes.
Inputs: Quarter, game clock, and the score of both teams at the time of the play. Garbage-time plays are not thrown out -- they count for 35% of a normal play in every "garbage-time-adjusted" figure, so a player who pads stats once a game is decided shows up as such rather than being invisible.
