Scarcely had his team secured a battling 2-1 extra time victory over Crystal Palace in the FA Cup final at Wembley before reports by BBC Sport
and Sky Sports
said he would be replaced as manager by Jose Mourinho later this week.
The Dutchman was in defiant mood when immediately questioned by the media, placing the famed trophy on the desk in front of him before reacting to the reports.
"I show you the cup and I don't discuss it (my future) with my friends of the media, who already sacked me for six months. Which manager can do what I have done?"
Asked if the victory could be the perfect farewell, van Gaal said: "I don't want to talk about leaving the club."
But Sunday, the UK's Press Association reported that he had refused to speak with a Sky Sports News reporter and said as he walked away: "It's over."
Manchester United has issued no statements about van Gaal's future and Mourinho's management team has not responded to a CNN request to comment on the issue.
Mourinho also refused to speak with reporters as he attended a boxing promotion in London Saturday night.
The Portuguese has been out of work since being sacked by Chelsea in December following a disastrous start to its English Premier League title defense.
At around the same time, the pressure intensified on van Gaal as Manchester United exited the Champions League at the group stages and started to fall off the pace in the English Premier League (EPL).
An eventual fifth place and defeat in the Europa League to arch-rival Liverpool, left the Red Devils unable to qualify for next year's Champions League and the riches that come with it.
Consolation has come in the form of the FA Cup triumph, but it may not be enough to allow the 64-year-old van Gaal to see out the final year of his three-year contract.
He took over from David Moyes after the Scotsman's disastrous tenure, the club slipping to seventh in the EPL after winning the title in Alex Ferguson's final year.
Van Gaal steadied the ship with a fourth place finish securing qualification for this season's Champions League, but results this campaign have been patchy and there has also been criticisms of the style of play adopted by his team.
Captain Wayne Rooney, who played a key role in the FA Cup win, jumped to van Gaal's defense Saturday. "I think it's a bit unfair after we've just won the FA Cup to speak about him as if he isn't here," he said.
"I think he's a good manager I'm grateful he's helped us win this FA Cup."
The club's Twitter account also posted a picture of van Gaal and Ferguson holding the cup together.