Antonio Brown's popping off at Tim Walz over his athletic background -- saying he's not a real football coach ... and, he couldn't take AB on one-on-one.
The former NFL star spoke at an Donald Trump event in Pennsylvania Saturday ... and, he took aim at Walz's time as a high school football coach -- kicking off by questioning his time on the sidelines at Mankato West High School.
ANTONIO BROWN: “And by the way, Tampon Tim Walz — he isn’t a real football coach.