The 22-year-old, who has pleaded not guilty, claimed he had thought Emile Walker, the man he confronted, was an armed mugger who wanted to steal his diamond-encrusted watch, valued at 64,000 pounds (131,000 dollars).
Walker claims that after he and Ferdinand had exchanged blows, he was forced to the ground by up to 10 men before escaping with a bruised jaw and a cut forehead.
In his statement to the court, Ferdinand said he left the club around 1 am and was kicked on the way out in the foyer.
When he got outside, there was a group of men "hanging about".
"I became apprehensive because one of the men began looking at me and my watch," he said in his statement.
"Although it was insured, I was worried in case the man might try to take it from me. The fear arose in part because I was mugged about a year ago in Croydon, during which my mobile was taken from me and a chain ripped from me. I found that incident frightening, and I try now to avoid having to go through that again."
Ferdinand told the police that a man - allegedly Walker - eyeballed him, at which a friend asked him what he was looking at.
"He said to my friend 'Is he for real? I will kill you,'" his statement said. "My friend got mad at being threatened like that. I told him to walk away. I was afraid there was going to be a fight, one I had not started, did not want and was trying to walk away from.
"I was worried he would take my watch by force, and I had worked hard to earn the money to buy that watch and did not want him to take it from me. The man who had threatened to kill my friend seemed to be acting on that threat by approaching us. For all I knew, he had a knife. It worries me people who are prepared to start a fight do not do so without carrying a weapon.
"Other people quickly became involved. I wasn't really focusing on anything other than protecting myself."
When asked whether he had thrown the first punch, though, Ferdinand admitted he had.
The case continues.