"I was behind it and I could see Jenas lying on the floor handling it. That's why I remonstrated with the linesman - how he didn't see it, I'll never know."
United were below-par for most of the game but Carlos Tevez rescued a point with an equaliser from a corner deep into stoppage time.
Ferdinand continued: "I remember going up for the corner and the referee said to me '30 seconds left', so I knew it was last-chance saloon.
"Luckily the ball in was good from Nani and Carlos was there to slot it home.
"We knew we had to come here and work hard. You need spirit if you want to win things and we showed that."