Man United were poor at Old Trafford and barely threatened the West Brom goal.
Chris Brunt grabbed what would be the winning goal for Tony Pulis’ side before Robin van Persie missed a penalty late on for United.
Van Gaal admitted he was disappointed with the result and that he needs to look at how his side can improve.
Speaking about the game, van Gaal said: “Only by communicating. The players are now very disappointed and the manager is disappointed.
“We have to evaluate what we are doing bad and what we are doing good and how we can improve.”
Out of ideas, out of creativity and out of guile, United can have no complaints with the scoreline.
The majority of fans were confident that United had qualified for next season’s Champions League following a recent six-game winning streak but the result has thrown United right back into the rat race. With three games to go between now and the end of the season, United cannot afford to slip up again.