Schweinsteiger came on as a half-time substitute in California but was largely anonymous.
Van Gaal said Schweinsteiger was “bad” during the match but insisted he is still working his way towards match fitness.
“The second half we played very badly. Schweinsteiger? He was also bad. Players can play bad, especially when they only have six days training in their legs and they have to play 45 minutes,” he said.
“Everyone can think it is easy to step in but it’s not. The first match he played very well and now he played badly, but that is also a process when you only have one week of training.
“We gave the ball away unnecessarily after half-time. Our positions in midfield were not as good as in the first half.”
Schweinsteiger has only been at United for a matter of weeks and he will have plenty of time to get up to speed.
Along with Memphis, Matteo Darmian and Morgan Schneiderlin, United’s new signings will all be afforded time to settle in before the new Premier League season kicks off in August. Hopefully then they will be able to hit the ground running.