The Go Ahead Eagles coach is a step away from being appointed by United as assistant coach.
The pair are close from their time together at FC Twente and Ten Hag has been effusive in his praise for Hake's coaching ability.
He said last year: "After our common period at Twente, we have always kept in touch. We meet up and call each other," the United boss explained last year.
"You talk about private matters, how things are going at home and with the children. But usually, it is about football. He was incredibly driven, ambitious, but also extremely convinced of himself (at Twente).
"He's a trainer with a CIOS background who worked very methodically. Rene had competencies that you do not learn on the football field."
Ten Hag also has said: "We think the same about many things in life and in football. At Twente, we worked together intensively, and we infected each other in the good sense of the word.
"As a result, you also drive each other to new insights and plans. This creates a kind of shared vision.
"We both love the game, and perhaps our working method is partly the same. We are both not averse to hard work."