The 18-year-old defender came on in the closing stages of United’s 2-0 win over West Brom to become the eighth academy graduate to feature for the first team during Van Gaal’s reign.
Van Gaal insists Borthwick-Jackson deserved his chance and revealed he had been tracking his progress in recent months.
“I have seen him once or twice and I have been impressed by him,” Van Gaal told MUTV.
“I talked with [Under-21s coach] Warren Joyce and asked what he had for me.
“I’m always talking with him or [Under-18s coach] Paul McGuinness, and he [Joyce] said at the moment the left full-back is in good shape.
“I put Cameron in the line-up without any fear, and I have to say he did very well.”