Van Gaal revealed after United's win over Liverpool in the US last Monday evening that he would soon decide on which players he wanted to keep at Old Trafford and which ones he wanted to let go.
Now, according to the Daily Mail, the Dutchman has held meetings with Rafael, Fellaini, Nani, Anderson and Hernandez to inform them they are not part of the first-team plans for the upcoming season.
The quintet have reportedly been told to instruct their representatives to find them new clubs before the transfer window closes in three weeks' time.
While Fellaini, Nani, Anderson and Hernandez were all widely expected to be part of the group told they could move on this summer, news that Rafael can leave will come as a shock, especially with Van Gaal favouring a 3-5-2 formation in pre-season.
The new United boss remains keen to strengthen his squad and is said to have made Borussia Dortmund's Mats Hummels his top target in central defence.
Juventus midfielder Artuto Vidal has also been strongly linked with a move to the club, although the Italians insist the Chile international will stay put this summer.