In his role as a Sky Sports pundit, Neville scathingly compared Van Gaal's United to a pub team following their highly fortuitous victory at St Mary's Stadium on Monday night.
Neville said: "I started laughing
It (the performance) was so bad."
Neville also said he was "shocked" by the poor passing on display from the Red Devils and claimed Van Gaal's players looked "shaky" on the ball.
"They've got away with murder tonight really with that performance," added the former United right-back, who played 602 times for the club.
Looking ahead to Sunday's game against Liverpool, Neville said the fixture could resemble "The Dog and Duck versus The Red Lion".
That did not go down well with United boss Van Gaal, who said the England coach "should pay more attention to his own words."
But Neville, United's fifth-highest appearance maker, played down talk of a rift between himself and the former Ajax and Barcelona manager.
One Twitter user asked Neville following the match: "@r1fgm: @GNev2 the press mentioning a feud between yourself and Van Gaal
What feud?"
And Neville replied: "One that will be created that doesn't exist."
Source: PA