In March of 2019, Drew Brees and the New Orleans Saints restructured his contract to a drop his salary from just over $33 million to roughly $25 million for the next two years, but they also added $21.3 million in dead money due to Drew Brees.
According to the NFL term dictionary, dead money “Refers to salary a team has already paid or has committed to paying (i.e., a signing bonus, fully guaranteed base salaries, earned bonuses, etc.) but has not been charged against the salary cap.
In business terms, it is essentially a ‘sunk cost.’
Any money a team pays a player must be accounted for against the salary cap.