Sir Alex Ferguson has described Louis van Gaal as a "formidable" manager, giving the new Manchester United boss his full backing.

The Dutchman took over the Old Trafford hotseat in the summer following the disappointing reign of David Moyes, which saw the club slip to seventh place in the Premier League table last season.

Despite a mixed start to life at United, Ferguson is adamant that Van Gaal has shown enough in the past to prove that he is the right man for the job.

"Louis is what I would call a managers' coach," the 72-year-old writes in his updated autobiography, Fergie. "He's one of those committed ultra-professionals. If I had to choose one word for him it would be 'formidable'.

"Football is his life. Wherever he has managed, every footballer will have learned from him. He was a good choice."

The Red Devils have won three of their eight league games so far this season.