OKC Thunder Player Gets Knocked the Hell Out ... By His Teammate!

OKC Thunder star Steven Adams knocked his teammate OUT COLD in a game last night ... but they weren't fighting -- Adams was literally standing still!

The bizarre play went down at the Chesapeake Energy Arena ... when Thunder rookie Terrance Ferguson tried to stay with his man on D.

Unfortunately, standing in his way was 7 feet, 255 pounds of chiseled Jason Momoa-looking muscle (Adams) ... and Ferguson's svelte 6'7'', 184-pound frame couldn't handle the business.

The 2 collided heads -- and DOWN WENT FERGY. Adams was totally fine, BTW.

Steven, being the good dude that he is, quickly got the rook some medical attention ... and it looks like Terrance is gonna be OK outside of a possible concussion.