The Red Devils head into their next encounter against Stoke City without a win in their last six games, the last three all losses to Bournemouth, Wolfsburg and, most recently, Norwich City.
His side's recent form isn't the only issue for Van Gaal, though, with everything from the Dutchman's decision making to his philsophies coming under heavy criticism from former players and pundits.
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His patient and rigid style of play has gone a long way towards tackling some of United's defensive frailties from the last two seasons, but a lack of goals and attacking threat has seen the Old Trafford side booed off the pitch come the final whistle recently.
And it seems patience is wearing thing amongst the hierachy in the red half of Manchester, with Van Gaal reportedly told a loss in either of his next two games will see his tenure come to a dramatic end.
After their away bout with Stoke on Boxing Day, United face fellow strugglers Chelsea at home in what could prove to be Van Gaal's most important - and potentially last - game as manager.
The former Netherland's boss has previously admitted he would resign if he felt he'd lost the belief and support of his players, and following his home defeat to the Canaries on Saturday conceded he was worried for his job.
Were the 64-year-old to be sacked, the list of potential replacements appears extensive. Pep Guardiola announced his plans to leave Bayern Munich at the end of this season earlier this week, whilst former Real Madrid and Chelsea manager Jose Mourinho has revealed his desire to manage the 20-time English league champions.
Whoever is in charge come the summer is reportedly in line to receive a £250 million transfer budget with which to improve the current squad.
United have been linked with a number of high profile players this season, including audacious moves for Madrid's Gareth Bale and Barcelona sensation Neymar.