As offenses have become more reliant on the passing game over the history of the NFL, wide receivers have become increasingly valuable. As such, their contracts have skyrocketed over time.
While there are an abundance of great receivers in the NFL, having an elite receiver has proven tremendously important for practically any offense, and especially ones looking to help out their quarterbacks. Just ask the Titans, who traded A.J. Brown instead of extending him and have yet to find a replacement with close to his impact.
