Forget Louis van Gaal's decision to stick with three central defenders, or his utterly bizarre choice to put Phil Jones on corners, it was his decision to deploy Angel di Maria as Manchester United's second-striker against Queens Park Rangers which should cause supporters real concern.
The most expensive player in British football history, at £59.7 million, was played in a totally alien position for the second weekend in a row. It was an experiment which failed to pay off against Southampton and, unsurprisingly, the same outcome occurred at Loftus Road.
Albert Einstein famously described insanity as doing the same thing over and over and expecting different results - but it doesn't take someone with a comparable IQ to the iconic German theoretical physicist to work out Di Maria is not a forward.
Di Maria is a central midfielder or winger
As the world-class Argentine proved last season: he works best from a deeper midfield role, where he is constantly facing towards the opponents' goal and looking to drive forward with purpose each time he receives the ball.
Failing that, the rest of his career has been spent playing from the wing. Di Maria is not, and never will be, an effective support striker - and the Manchester United supporters will be hoping Saturday's performance will convince Van Gaal to switch his position with that of Wayne Rooney, a player blessed with the underrated ability to make the ball stick.
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Wayne Rooney mystery
Rooney is the third highest goalscorer in United's history - and the striker who looks certain to become England's record goalscorer before the end of 2015.
Yet Van Gaal, inexplicably, feels Manchester United's number ten is more effective in a deeper role. He does not believe Rooney is a natural striker - and publicly admitted as much earlier this season.
Di Maria at risk of becoming the next Ozil?
But back to Di Maria, who is in danger of going down the same ill-fated path as his former teammate Mesut Ozil if Van Gaal continues mis-using him. There are plenty of comparisons to make between the two players.
First of all, both sealed unexpected moves from Real Madrid to the Premier League towards the end of the summer transfer window for record fees.
Both enjoyed eye-catching starts to they respective spells in the Premier League before a combination of poor form and injuries began to have a negative impact on their confidence levels.
Both have been played out of position by their managers - Di Maria as a second-striker and Ozil on the left wing at Arsenal - and both have failed to hit top gear since leaving the Bernabeu.
Van Gaal must start using Di Maria correctly
Ozil is now a shadow of his former self - and there's a danger that the same thing will happen to Di Maria unless Van Gaal starts playing him in his natural position.
If Di Maria fails at Old Trafford, Van Gaal will have nobody to blame but himself.