The match official, who has now sent off seven players from English teams, made headlines for controversially giving United winger Nani his marching orders for a high challenge on Alvaro Arbeloa during the Red Devils' 2-1 defeat at Old Trafford on Tuesday.
"I was concerned," Ferguson said in a press conference. "I said that to my staff. I had a big worry about it but it is gone now. There is nothing we can do about it."
Cakir has since been the subject of hate pages on social network website Facebook.