John Daly -- What Collapsed Lung?! ... Sings Heart Out Days After Medical Scare

John Daly was singing at the top of his lungs last night ... which is miraculous considering one of them had COLLAPSED just a few days ago.

The golf legend grabbed his guitar and hit the stage with Mark Bryan from Hootie & the Blowfish to sing "Knockin' On Heaven's Door" in Myrtle Beach last night.

Dude sounded GREAT in front of an audience that included former Golf Channel host Win McMurry.

But what makes this video so impressive -- Daly reportedly collapsed and was rushed to a hospital on Saturday during a golf tournament. In fact, one report says the situation was so dire, Daly wasn't breathing for 3 minutes and needed CPR to revive him.