The Spain international made key saves from Raheem Sterling and Mario Balotelli at Old Trafford to help the Red Devils to a sixth consecutive win which moves then 10 points ahead of Brendan Rodgers's side.
De Gea has been linked with a move away from the club, with Real Madrid reportedly interested, and Van Gaal refused to answer questions concerning contract talks between the goalkeeper and United.
"I don't think you [the press] need to be acquainted with those types of things," he told reporters after the match. "That is between club and player and not open to discussion with the media."
Van Gaal also played down his goalkeeper's recent heroics, insisting that his team's recent good run is down to the collective and not individual displays.
"I think the team has done very well and De Gea contributed a big part of that," he added. "I am not cautious to praise David De Gea but every individual player.
"We are doing it as a team, not one player is winning. I can mention other players and their performance was always high.
"I have seen more than three players who were very good today, that is why. He is fantastic [but] I want to mention the team instead of an individual."