Mata was largely anonymous against Sheffield United until he was replaced in the 60th minute by Memphis Depay, who went close with a long-range effort before winning a penalty in the third minute of added time.
“We have to play with wingers who make the pitch as big as possible and with Memphis and [Jesse] Lingard I know it’s like that. So we improved by restoring the shape,” Van Gaal said.
“I asked Mata but he was never there.
“Then [Matteo] Darmian has to be the right winger and he tried to do that but that is not his speciality and that’s why I changed.”