Pietersen claimed that "it's tough being me in this dressing room" during the Test series against South Africa in the summer and Prior has admitted that it was that revelation that prompted him to call his teammate.
The wicketkeeper told The Sun: "When he said 'it's tough being me', I thought 'hang on, something is not right here when one of our senior players is struggling.'
"So I just wanted to know what KP was thinking — whether he did have gripes with the dressing room. We've been hit hard with this stuff and people will think our team spirit is not what it was made out to be. But I genuinely believe in this team.
"It's easy to look after each other when we're winning, but it's when things are don't go well that you have to protect the team spirit and protect each other."
Pietersen could return for this winter's tour of India if ongoing talks with the ECB are successful.