Louis van Gaal has been in charge of Manchester United for over seven months but he admits he still does not his best starting XI or formation.

United may be third in the Barclays Premier League, but that has not saved their manager from criticism.

The first signs of unrest came last month at QPR when United fans demanded Van Gaal ditch his three-man defence by chanting "4-4-2".

The 63-year-old has acquiesced to their demands in recent weeks, altering the formation to a 4-4-2 diamond, but he concedes that even though the season is nearly three quarters of the way through, he still has not found a settled line-up.

"No, I don't think so," Van Gaal said when asked if he had found the right balance in his team.

"I have played now already five or six systems and I am looking still for the balance. But this system is more attractive than normally and I can play with more attacking players.

"That's the reason I am doing that.

"In spite of the fact that we are looking for the balance, our results are not bad and our defensive organisation is not bad, we also score a lot of goals. So, I cannot say that I am very disappointed about that. But we have to do it now, and normally you have to do it pre-season."

Paul Scholes, Sam Allardyce and Falcao's agent Jorge Mendes - among others - have been forthright critics of United in recent weeks.

Scholes, writing in the Independent, said some of United's play under the Dutchman had been "miserable" and complained that strikers Robin van Persie and Falcao looked like "strangers" against Burnley.

Allardyce branded Van Gaal's team "long-ball United" and even veteran Preston striker Kevin Davies mocked the former Bayern Munich coach ahead of Monday's FA Cup tie with the Red Devils at Deepdale.

Van Gaal insists neither he nor his players will lose any sleep over the recent criticism though.

"I don't worry about it, it's not so interesting I think because he (Paul Scholes) is one of the fans, I hope, and he can criticise," the United boss said.

"Fans can criticise, and that's not a problem.

"I am used to it and I think all the players are used to it because they are professional football players.

"Maybe some players are affected, but normally most of the time it does not affect me or the players."

Van Gaal hopes to bring a smile back to fans' faces by recording a comprehensive win at League One Preston in the fifth round of the FA Cup.

Van Persie is a doubt for the match at Deepdale due to an unspecified injury, and Phil Jones also looks likely to be absent due to the knee problem he suffered against the Clarets.

Daley Blind could return after hobbling off in the midweek win with a head injury but Michael Carrick has suffered a setback in his recovery from a calf injury and will not feature.