The boxing legend cracked Cash Wheeler right in the face with a hard right hand during a ringside encounter ... sending Wheeler crashing to the floor like a sack of potatoes.

It was awesome!!!

In fact, just listen to the sound of the contact -- yeesh!!

Here's the backstory ... Inner Circle's Chris Jericho was taking on The Pinnacle’s Dax Harwood in a heated 1-on-1 march -- and before the opening bell, Mike vowed to keep the peace by any means necessary.

Long story short, Cash Wheeler tried to interfere with the match to help his tag team partner Dax. At one point, he even grabbed a baseball bat in hopes of taking a swing at Jericho.

... and that's when Iron Mike came around the corner and gave him the ol' Michael Spinks treatment (Google it).

Ultimately, Jericho got the win -- and thanked Mike for having his back and included Mike as an auxiliary member of the Inner Circle.