Warnock, whose excellent new book, The Gaffer, was published on Thursday, is a big admirer of Sir Alex Ferguson's successor at Old Trafford.
"I didn't think David would get the job," Warnock told the Mirror, "but I was delighted when he did.
"Jose and Wenger and Manuel Pellegrini, at Man City, might think his appointment gives them an advantage, but I think the opposite.
"I think David will get a new lease of life from getting the United job. It will make him work even harder than before.
"It will rekindle his determination and he will revel in the new job. He will have so much enthusiasm and so much hunger to succeed.
"He will make it more difficult for his rivals than anyone else could have done because of the desire he has got."