It's tough but eventually it happens to almost every player. Even Jr.Seau left San Diego. Really makes it hard for players and teams to remain on good terms at the end of their careers.
RM was a great guy to have at MLB when the Cards DLine was so weak they had to have someone who could run guys down from behind or sideline to sideline. But now they need someone who can fill the holes, blow up plays at the line of scrimmage, and help out in pass coverage and McKinnon has never been very good at doing that.
Defensive rank in yards allowed during RMacs time with the team:
19,26,21,22,26,27,29,25,12. Points allowed is even worse never ranking higher than 22nd until 2004.
We'll never know how good he really was as he played on probably the worst group of defenses ever assembled in the NFL.