"I think we froze and we are massively disappointed," Southgate said after the 2-0 defeat at The Riverside.
"We just didn't do it. We haven't performed well enough. Cardiff out-performed us and we can have no excuses.
"We are going to get slaughtered, and rightly so.
"We have to take it on the chin. The fans are rightly disappointed and angry.
"The only way we can answer the criticism that is bound to come our way is on the field.
"I've clearly not got it right today because we haven't won. That's my responsibility."