The Both Sides Now singer was hospitalised in Los Angeles in May (15) and now the Crosby, Stills & Nash star is speaking out about her health drama, explaining, "She took a terrible hit".
The rock veteran tells the Huffington Post, "Nobody found her for a while."
Updating fans on her current condition, he adds, "To my knowledge she is not speaking yet... She's going to have to struggle back from it the way you struggle back from a traumatic brain injury.
"She's a tough girl, and very smart. So, how much she's going to come back and when, I don't know and I'm not going to guess."
Little has been released about Mitchell's health through official channels, but days after she was hospitalised, her aides released a statement which read: "Joni remains under observation in the hospital and is resting comfortably. We are encouraged by her progress and she continues to improve and get stronger each day."
And Crosby is hopeful his friend can recover, adding, "I love her. She's probably the best of us - probably the greatest living singer/songwriter."