In training sessions he openly criticised his players if he thought they were not up to scratch.
Van Gaal had some stern words for Wayne Rooney on a couple of occasions, but the England striker has no qualms with the Dutchman's hard-line approach.
"He is a tough but fair manager," Rooney said.
The former Everton striker thinks the new coach has made a big impact at the club.
"He has been great," Rooney added.
"Since he has come in he has given us all a different way of looking at football, so it's been great for us and hopefully that will continue."
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