The actor worked with Scott on five movies, including Crimson Tide, Man on Fire and The Taking of Pelham 123, and they had started planning another just one week before the Top Gun filmmaker jumped from a bridge in California.
Washington couldn't understand why Scott would take his own life, and admits the tragedy prompted him to reflect on all their previous conversations.
He tells Britain's Seven magazine, "I made five movies with him. I talked to him about a week before he died about our sixth movie. He wanted to do a film where I played a submarine captain driving a submarine filled with narcotics. We were talking about it.
"I've never been in a situation like this where you start to backtrack. You think what they said to you. You think what you said. And then a week later they kill themselves. You might think it was something that I did. You don't see it coming. I don't know what was going on in his life."
The Oscar winner now has no interest in pursuing the submarine project with another director, adding, "I wouldn't touch it now. Not without him."