Guitar legend Joe Satriani spoke in a livestream on Facebook and explained the real reason that why he quit from Deep Purple. He said (transcriped by Ultimate-Guitar):

“If I could have I would have. But they really sort of borrowed me out of my solo career just as it was really entering a very interesting phase.

And I didn’t think that I’d be able to really give them 100%, and that’s what they needed. They were replacing Ritchie Blackmore and they needed someone who was a 100%. Thank god they found Steve Morse because he was a genius.”

You watch the Deep Purple’s live show that including Joe Satriani from below.