Here's JuJu Smith-Schuster eating over TWENTY punches from boxing superstar Ryan Garcia for a "body shot challenge" video ... just days before he's set to sign a new, mega-contract!!

JuJu -- who will likely move on from the Steelers and ink a multi-million dollar deal with a new team later this month -- decided to hit the gym with Garcia and take a pounding.

If you're unfamiliar, Garcia has made the "body shot challenge" famous over the last few months ... both taking and giving punches to and from celebs in wild, viral videos.

To his credit, JuJu held up pretty well despite the barrage of violent left and right hooks from one of the world's best boxers ... but in the end, the NFL wideout was hit so many times, he crumpled to the ground.

Don't worry, the 24-year-old is going to be okay -- at least, it appears that way -- he posted on social media afterward, "Amazing workout with @kingryan, so much respect for Pro Boxers! This was no joke!"

Garcia also commented on the clip, joking he KO'ed one of the NFL's best receivers!

"DOWN GOES JUJU 🗣 😂😂 Body Shot Challenge claims another 🥊🥊 Respect to Juju for doing it with little to no protection."