The biggest cap hit in AD's extension comes in 2021 when he is 30 years old ($27.892M)
The second biggest hit is in 2020 when he is 29 ($25M)
His cap hit decreases when he is 31, 32, & 33 to $22.25M, $19M, and $21.75M
He is not under contract after that.
It wouldn't surprise me if AD performs at a pro-bowl level (or better) all thru this contract. And it also wouldn't surprise me if this contract looks like a bargain in 5 years. But if not the Rams could cut him after the 2022 season with no cap implications.
In effect AD has a 4-year, $101M contract and the Rams have the option of paying him $19M for 2023 and then have the option of paying him $21.75M for 2024.
AlbaNY_Ram