And now Murphy's Law has got in on the act.
"I think it's the law of Murphy," Van Gaal said after Thursday's shock 2-1 Europa League defeat by FC Midtjylland, referencing the old adage that anything that can go wrong, will go wrong.
True, United may have lost star goalkeeper David de Gea to injury in the warm-up, but it's not the first time this season that Van Gaal has attempted to shift the blame -- and his excuses are starting to wear thin with supporters.
And with speculation growing over Jose Mourino taking charge at Old Trafford, Thursday's humiliating defeat couldn't have come at a worse time for Van Gaal.
The Dutchman will want to make sure United avoid the embarrassment of slipping to another loss at League One side Shrewsbury in the FA Cup fifth round Monday -- just what would his excuse be if the unthinkable happened in England's premier cup competition?
CNN Sport takes a look at some of Van Gaal's best excuses this season.
Other clubs' spending
Thursday's loss was United's 11th of the season -- an unthinkable statistic just a few years ago -- while it remains six points off the Premier League's top four in the chase to qualify for the Champions League.
And if that wasn't problematic enough, the club is playing some of its dullest football in recent memory to boot.
But Van Gaal doesn't seem to believe the problem is an internal one -- rather his reasoning for his side's underachieving is down to the other clubs spending too much money.
"Now we have much more clubs who have the money and are able to win something," he said in December. "Every club can buy a player. The difference is not so big any more. The confirmation is every week -- the bottom clubs can beat the top teams."
Note to Van Gaal -- according to Forbes, United are worth $3 billion, while under the Dutchman the club have spent in excess of $350 million on new signings.
Paul Scholes
Van Gaal has come under fire from all angles this season for United's slow and insipid style of play -- and one of the Dutchman's harshest critics has been a certain Paul Scholes.
The United legend, in his role as a media pundit, has frequently picked holes in his former side, even labeling the Red Devils players "bored" of their own manager.
Scholes' words have not gone unnoticed by Van Gaal, who feels the ex-England international's opinions are doing more harm to United's chances of success on the pitch than good.
"In England, it is more the result than performance, only when Paul Scholes started he influenced a certain amount of fans," Van Gaal said.
"What Scholes is thinking, he has to think it. But my problem is when you create an atmosphere, a very negative atmosphere for somebody, so maybe he should be more positive," added Van Gaal.
Referees
For United fans, being absent from the Champions League last season for the first time in 19 years was a bitter pill to swallow.
That Van Gaal swiftly brought elite-level European football back to Old Trafford at the first time of asking helped to ease the pain -- only for his side to no sooner undo all of its good work by bowing out meekly in the group stage this term.
United were strongly fancied to escape from a pool containing Wolfsburg, PSV Eindhoven and CSKA Moscow, but a record of two wins from six games was poor enough to ensure it missed out on a place in the knockout rounds.
Van Gaal's reasoning behind the early exit?
It wasn't down to poor performances or bad results, but rather some questionable refereeing.
"When you overview everything you remember the first match against PSV with the decisions of the referee and also today against Wolfsburg -- they were not positive for us," he said.
Journalists
The football journalist has not been Van Gaal's best friend this season.
Those attending a Christmas Eve media conference were not treated to holiday cheer and goodwill, but rather Van Gaal marching out of the room spouting sarcastically "enjoy the wine and a mince pie" after becoming angered by speculation about his future.
One writer, meanwhile, was even labeled a "fat man" by the Dutchman during another media conference in January following his criticism of United captain Wayne Rooney.
"I want to say only that I have tried to lift the confidence of my players, I have done everything this week," Van Gaal said in December after a run of six games without victory.
"I hold meetings, evaluation meetings with the players, with my members of staff, I hold a Christmas lunch, I have held a speech and I feel the warmth and support of everybody in Carrington, the AON training complex. But I don't feel that in the media."
It's the result that counts
Manchester United fans are used to winning the Manchester United way.
The club's success over the years has often been borne out of its sides playing attractive, attacking football -- standards the current team has struggled to match this season, particularly in the FA Cup against Sheffield United.
United kicked off its cup campaign this year against the League One outfit and although Wayne Rooney eventually secured a 1-0 victory with a late penalty, the home team were roundly criticized for a display bereft of any creativity or flair.
Van Gaal, however, was happy to excuse the poor performance given his side had advanced to the next round.
"I said to the boys, 'The only thing that counts is we are in the fourth round', and we did it," he said.
Van Gaal can't play himself
United's struggle for goals this season has been well documented.
Nine more teams have bettered its tally of 33 goals in the Premier League this term, while up until earlier this month, it had gone a whole eight hours and 40 minutes without a first-half goal at home.
But, according to Van Gaal, there's one underlying factor behind his side's form in front of goal -- he can't play himself up front.
"When you say I am hired to make the difference, you are right," he said. "I can make the difference, in tactics and everything, but I cannot score goals."
