According to ESPN, McDonald's contract -- a two-year, $7 million deal he signed in March as a free agent -- required him to pass a June 11 physical in order to guarantee all $3 million of his base salary.
The 31-year-old had shoulder surgery earlier this offseason, and Tuesday's news likely means he remains unable to pass a physical.
McDonald can still make up the $2 million trim to his base salary through weekly roster bonuses pertaining to his status on the 53-man roster and whether or not he is active on gamedays, per ESPN. He is still guaranteed $1 million in base salary and a $1 million roster bonus, making for a maximum of $4 million in earnings in 2018.
McDonald had 5.0 sacks for the Tampa Bay Buccaneers last year, the third time he has topped that figure in a single season in his career. He has 19.0 sacks in 97 games (36 starts) across nine NFL seasons.
--Field Level Media