The Spaniard, who is wanted by Real Madrid, produced a strong performance as goals from Wayne Rooney, Jesse Lingard and Adnan Januzaj at the Levi’s Stadium – home of the San Francisco 49ers – maintained United’s 100 per cent tour record.
De Gea denied Sergi Roberto a goal when the Barcelona midfielder was clean through in the first half, and grew in confidence from there on.
After the final whistle, Van Gaal saluted his goalkeeper, who has been out with a back injury, and reiterated that he wants him to stay at Old Trafford for next season despite Madrid’s interest.
“Of course I do hope that David de Gea shall stay but in this world of football you never know,” Van Gaal said.
“In spite of his injury he doesn’t train for one week, he can show his quality already in this game.
“He has showed his quality.
“The first chance was for Barcelona. When you stop the first chance, then you can score the first goal, which we did. That is always the difference in the game.”
Van Gaal said Barca, who were without Lionel Messi and Neymar, could not deal with the danger posed by Rooney and Memphis Depay, who played in the No 10 role just behind the skipper.
“I think they are always a threat,” Van Gaal said.
“That is very important. Barcelona could not cope with the threat of Depay and Rooney.”
Van Gaal also praised Januzaj, who scored United’s final goal in injury time after coming on as one of 11 changes on the hour.
“Adnan Januzaj was very good,” Van Gaal added.
“He always gives an option for his midfielders and defenders and scored a wonderful goal.”
Luis Enrique said if it was up to him, Barca would not have even played the match in the US.
“As a coach I would prefer not to do tours. I would prefer to stay closer to home,” said the Barcelona manager, who now takes his team to Washington DC to face Chelsea.
United, meanwhile, will round their tour off against PSG in Chicago in the early hours of Thursday morning.