The city has been counting the days to the visit of Wayne Rooney and company since the fixtures were announced in June, and the occasion gives Williams the chance to get one over on United stalwart Ferdinand.
The 26-year-old shares the same agent as Ferdinand, but is keen to make sure any niceties are saved until after the final whistle, and said: "It's a game that you look for when the fixtures get drawn and I can't wait. I haven't spoken to Rio but I will probably message him before the game."
He added: "We have got the same agent. I first met him through the agency and it developed from there.
"We all went away together in the summer and got to know each other. He is one of the world-class defenders at the moment.
"He's a cool, funny guy, but quite normal. I am looking forward to playing against him. But there will no banter until after the game."
The contest will also pit Williams against Rooney for the third time in 2011. The former Everton striker emerged on the winning side in the two Euro 2012 qualifiers between England and Wales, and Williams is hoping it will be third time lucky, although he acknowledged the class of the United man.
"Wayne has got obvious quality and his movement is difficult for anyone to deal with," he said. "He has great movement but you have to be on your game and hope that he is not firing on all cylinders.
"He would be one of the most difficult opponents I have played against.
"Obviously we played against each at Wembley and he is a difficult player to mark. But, Saturday will be different because he plays differently for Manchester United than he does for England."
Source: PA
Source: PA