Manchester United manager Louis van Gaal defended the use of his 3-5-2 system after criticism from sections of the away supporters in Saturday's 2-0 Premier League win at QPR.
United ended a run of three league matches without a win as substitutes Marouane Fellaini and James Wilson scored in the second half to clinch all three points at Loftus Road.
However, it was a somewhat disjointed performance from United and some fans started chanting "4-4-2" in an apparent attempt to get Van Gaal to switch shape.
The Dutchman acknowledged that his side created more chances after changing tactics with the score at 1-0, but believes the defensive strength of his side is compromised when he plays four at the back.
"I know in advance when we play with four midfielders in a diamond that we create more chances," Van Gaal said.
"But then the balance of the team is also weak. And you see it because we have created chances but also Queens Park Rangers have, and we have to decide every week how to play. That's the question.
"But with the other system [3-5-2] we played against Tottenham, maybe you remember the first half - we created six or seven chances more than today and we did not score.
"So it's always the question - are you effective enough?"
Van Gaal recalled Radamel Falcao to his starting XI in the absence of injured Robin van Persie.
Earlier this week Van Gaal challenged the Colombia international to prove his worth to the team and though praising a decent showing, he stated the former Atletico Madrid man should have scored in the first half when he was denied by Rob Green at close range.
"In the first-half, I think we created one chance and I think Falcao has to score," Van Gaal added.
"But in the second-half I think Falcao was also three times [involved] with big chances and we scored two goals.
"It's not so important what I think because he wants to score goals and for me I have to judge how he has played and scoring goals is an important aspect of a striker, I know."
