Ferguson will use dad Alex's FA Cup misery to try to inspire Preston to a shock fourth-round triumph.
He said: "Sometimes you get years when there are little flurries of shock results.
"Those are the examples you need to look at. Leeds going to Old Trafford and Reading going to Anfield and winning.
"It happens all the time in the FA Cup. It's why it grabs everyone's emotions.
"Chelsea can't play well every game. If we are at our maximum and they are not, we stand a chance."