The Scotsman is back in contention after a lengthy period on the sidelines due to his bowel condition ulcerative colitis.
"The sooner the games come around, the better," Sky Sports News quotes Fletcher as saying. "Every opportunity you get you have got to show you are good enough and capable of being in his plans for the rest of the season.
"It is a fresh start - go and impress him as soon as possible and get your name in the team and in the squad for the next season. I think it is going to be exciting times again."
Van Gaal will begin his role with the former Premier League champions following the Netherlands' World Cup third-place playoff against hosts Brazil on Saturday.