The two were together with the Dutch national team before Van Gaal joined Van Persie at United by replacing David Moyes in 2014.
Most expected the two to continue their fruitful relationship, but Van Persie was moved along after one season by Van Gaal.
"I had this chat with Louis van Gaal and he told me: 'Ok Robin, our ways will part. I'm the coach, you're the player - you have to go, your time is up'," Van Persie told the High Performance Podcast.
"I was like: 'Yeah but I still have a contract?' He said: 'I don't care'.
"Ruthless. Towards the end of it, I saw something coming but not this ruthless. And the way he said it as well. And then, like a lot of things go through your mind when you get a message like that.
"I still had a contract, my family was happy, it was my 11th year in England. We love living in England. What's next?
"My kids are going to school, they have their friends and everything. So in like a split second, all these things come across [your mind]. How do you react to that?
"I said: 'We will see what happens. That's your opinion. But I have a contract and I'm happy in England at Manchester United. So we will see what happens'. And I stood up, shook his hand and left it."