The 29-year-old's dynamic displays have added an extra edge to United in the same way that French playmaker Eric Cantona and Portugal forward Cristiano Ronaldo galvanised previous teams in the Ferguson era. After missing out on the title to City last season, United were in need of a new driving force this term and Ferguson believes van Persie is providing it.
"I am reluctant to subscribe to the cult of an individual. But sometimes you find the last piece of the jigsaw," Ferguson told United's official matchday programme. "We did it when we brought Eric Cantona to Old Trafford and he proved to be the right player at the right club at the right time. He became the catalyst and springboard for our surge to success.
"It doesn't have to be signing someone for a record fee. Cristiano Ronaldo was not a record buy either but he certainly made a difference as he prospered with us to the extent that he came to be regarded by a lot of people as the world's best player."
Without van Persie's goals, United would be eighth and that perhaps explained Ferguson's fury when Swansea defender Ashley Williams kicked the ball into the Dutchman's head as he lay prone on the turf during Sunday's 1-1 draw at the Liberty Stadium. How Manchester City manager Roberto Mancini must rue van Persie's decision to snub the champions in favour of joining United.