Dolphins coach Brian Flores told reporters it was a "tough decision" and one his staff and the front office "went back and forth on."
"I have a lot of appreciation for his hard work. There is a lot that goes into it. Position, salary cap, kicking game," Flores told reporters, according to the Miami Herald.
Linebacker Elandon Roberts returned from the physically unable to perform list last week, contributing to the decision. McKinney had been starting at inside linebacker while Roberts was sidelined. Now Roberts and Jerome Baker will be the team's starting inside linebackers.
The 28-year-old McKinney, a Pro Bowler in 2018, played in only four games in 2020 before undergoing shoulder surgery. He has posted 100 or more tackles in three of his six seasons and has 530 tackles and 11.5 sacks in 80 games.