Bears' Zach Miller Retires After Horrific Leg Injury

Zach Miller -- the Chicago Bears tight end who nearly lost his leg in 2017 after suffering a horrific injury -- says he's done with football ... announcing, "The time has come."

Miller severely mangled his leg during an Oct. 29, 2017 game against the New Orleans Saints ... when his left knee snapped as he tried to haul in a TD pass in the 3rd quarter.

The injury was gruesome ... his knee dislocated so severely that vascular surgeons were called in to help repair a damaged artery.

You can watch the video here ... BUT WHY WOULD YOU DO THAT TO YOURSELF?!

Docs were able to save Miller's leg ... and the 34-year-old tried to make an NFL comeback -- but he announced Tuesday he's officially callin' it a career.

"I would love more than anything to step on Soldier Field one last time but I physically cannot give the game and our fans what they deserve," Miller wrote.

"It’s difficult to find words to express my love and gratitude to every single person that has cheered my name, picked me up and stood strong with me throughout my time in this league. I am forever grateful."