Ex-NFL Lineman -- Warns Kyrie Irving ... Don't End Up Like Me!

A former NFL lineman has a STERN WARNING for Kyrie Irving ... don't let the doctors pressure you into coming back early ... or you could wind up with an OBLITERATED KNEE!!!!

The man behind the warning is LeCharles Bentley ... a former 2-time Pro Bowler who played for the Cleveland Browns ... who suffered a pretty major knee injury of his own during his playing days.

As for Kyrie -- the Cavs said he'd been suffering from a "bad case of tendonitis" over the past few weeks and wanted him to play last night. Kyrie's father had reportedly been pushing for Irving to take it easy.

Enter Bentley ... who added his perspective on social media after the game:

"So the doc tells Kyrie it's 'just tendonitis' ... Yea, I tore my patella from having 'just tendonitis'. I tried to 'tough it out'... ."

He then posted a picture of what his knee looks like now -- and said, "Oh, 'it just tendonitis'... I'm out, about to go 'tough out' this leg workout. Could be worse! #Blessed."

Bottom line -- Bentley says, "Athletes better listen to their bodies, not Twitter & Docs."