Speaking in his role as a Sky Sports pundit after United's scrappy 2-1 victory at Southampton on Monday, Neville claimed Van Gaal's side had "got away with murder" by taking all three points after a below-par showing at St Mary's Stadium.
Former United captain Neville went on to jokingly suggest that Sunday's clash between his old club and arch rivals Liverpool, who drew 0-0 with Sunderland in a dour game at the weekend, could be akin to watching "the Dog and Duck versus the Red Lion" in a pub match.
But Van Gaal - whose side are now third in the Premier League after five straight victories - appeared to bristle at Neville's comments in his post-match media conference, despite admitting United were "lucky" to beat Southampton.
When informed that Neville had said United "got away with murder" before adding that this Sunday's fixture between English football's two most decorated clubs will be of average quality, Van Gaal responded: "With murder? That's an English expression? Maybe.
"He can say everything because he is an ex-legend, but as an ex-legend, or a legend you have to know what you are saying.
"That I have already said. You can interpret that, make an interpretation of that. It's not so difficult to make that interpretation.
"When I say that he has to pay attention to his words."
Neville attempted to quell any notion of a problem between himself and Van Gaal on Twitter after Monday's match, saying the media are attempting to make something out of nothing.
"One that will be created that doesn't exist," he replied to a query about whether he and the Dutchman are emroiled in a feud.
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