Benitez, who got to two Champions League finals with Liverpool, winning once, has agreed to take the job until the end of the season initially.
And he has a chance to lead the Blues to World Club Championship glory in Japan next month. Ferguson said: "It has proven that someone always wants a job. Rafa Benitez is prepared to take it short term.
"It shows you his eagerness to get back in. Football people are like that.
"They want to get back in, they want to manage even though they know there are pitfalls.
"It is not an easy job today. Expectation levels are never met."