Manchester United vs Chelsea: Louis van Gaal ready to use 'iron shield' against criticism of his philosophy

Louis van Gaal will put up his "iron shield" and do battle with those who criticise his methods at Manchester United.

Van Gaal faces the biggest test of his reign as United boss on Sunday when unbeaten league leaders Chelsea come to Old Trafford.

United's pre-season record under Van Gaal was impeccable, but since then the Red Devils have only taken 12 points from a possible 24 to lie sixth in the Barclays Premier League.

Van Gaal's decision to play 5-3-2 at the start of the season was heavily criticised and he also came under fire for failing to add any experienced defenders to his squad.

A third league defeat of the season, this time at the hands of his former protege Jose Mourinho, would lead to further criticism of his reign, but Van Gaal is not interested in what his doubters have to say.

"Maybe you know that I am always a controversial person and a lot has written about that, but I (have) an iron shield," the United boss said.

"It's been like that since I came to England.

"Everyone can write or speak about me and I cannot change that.

"It took a long time for me to understand but I cannot change that.

"I have learned not to react and to believe in myself, my players and staff. That's important."

Mourinho, who worked under Van Gaal at Barcelona for three years, employs a different tactic when it comes to criticism, often taking his enemies on in public spats.

Just last season he branded Arsene Wenger a "specialist in failure" for his lack of success at Arsenal.

Van Gaal refuses to go down the same route as his former assistant though.

"Every human being reacts, as I have said, in his own way and you have to ask him why he reacts like he does, not me," Van Gaal added.

"We hardly speak to each other. Sometimes on SMS."

With Mourinho by his side, Van Gaal won two Primera Division titles and the Copa del Rey during his first term at Barca.

Mourinho has since forged a hugely successful career of his own which has yielded an astounding 20 trophies to date.

The Portuguese often credits a lot of his success to Van Gaal and his other mentor Sir Bobby Robson, but the Manchester United manager thinks the main reason behind Mourinho's success is the man himself.

"He talks about Louis van Gaal and also Bobby Robson, and I appreciate that, but you always do it by yourself," Van Gaal said.

"It's good that Jose Mourinho's eyes were very open when he was my assistant, but you do it by yourself."

Mourinho has riled many leading figures in football, whether it be in Portugal, Italy, Spain or England.

The 51-year-old has been viewed as a somewhat arrogant figure ever since he proclaimed himself the 'Special One' when he arrived at Chelsea 10 years ago, so it was with some surprise that Van Gaal chose to describe Mourinho as "modest" on Friday.

"He is a very modest and emotional human being, and I like that," Van Gaal said.

"He's very special but he is very special for me because I've worked with him and we've continued our relationship, which in the football world is not always normal. That's nice."