Macklemore -- one of the biggest Seattle Seahawks fans alive -- says it would hurt his heart if Marshawn Lynch signed with the New England Patriots. 

The Boston Herald is reporting that Lynch has privately expressed interest in playing for the Pats if he can't reach a deal with the Oakland Raiders ... and Mack no likey.

Macklemore says he understands if Lynch signs with another team ... BUT NOT THE PATS!!

Obviously, shades of Super Bowl 49 still haunt him.