Today, Mourinho described Van Gaal's influence as "important" to his career after he worked as the Dutchman's assistant boss at Barcelona.
In response to his comments, Van Gaal has claimed that it is "fantastic" to see the Portuguese coach, who has won seven league titles and two Champions League trophies in his career so far, doing well.
"I was also an assistant coach and my eyes were also opened and it's good that his eyes were open when he was my assistant, but you do it by yourself," Van Gaal told reporters. "He's a wonderful coach and to see him as a coach winning trophies in other countries is fantastic."
United currently sit 10 points behind league leaders Chelsea.