- Premier League
Ferguson: Van Persie could have broken neck
The incident took place after referee Michael Oliver had stopped play with Williams claiming he hit the Dutchman accidentally, aiming to clear the ball in frustration.
Van Persie suffered no serious effects from being hit but Ferguson was incensed calling it "the most dangerous thing I've seen on a football field in many, many years."
The match resulted in United's lead at the top of the Premier League being cut from six points before the weekend to four over Christmas after Manchester City beat Reading on Saturday.
United had the better chances in Swansea but, with the exception of a well-taken goal from Patrice Evra, they could not convert them leaving Ferguson aggrieved.
"We absolutely battered them and we are very unlucky," Ferguson told Sky Sports. "It was just one of those games, he is a young referee, but really, what a performance. It should have been six point gap and that is the disappointment.
"Robin van Persie is lucky to be alive. It was a disgraceful act from their player and he should be banned by the FA. Robin could have had a broken neck."
After the game Williams offered his version of events. He said: "I just cleared the ball with frustration and unfortunately it hit him in the head and he got a bit angry about it. Everything got a bit heated but it was alright in the end."