Zat Knight has admitted that Aston Villa have 'not been good enough' at the back in recent games.
Villa have collected just two points from their last seven Premier League matches, failing to keep a clean sheet in the same period and conceding 18 goals.
They have continued to carry a threat in attack and Knight accepts that the defensive unit must shoulder a lot of the responsibility.
Martin Laursen and Wilfred Bouma have both been absent with long-term injuries but Knight is not looking for excuses.
"It's frustrating what has been happening - especially as a defender," said the former Fulham man.
"Your main aim as a defender is to go out there and keep a clean sheet and, we fail to score at the other end, that's not our problem. Our problem is the back.
"It is frustrating and it's just not good enough is it?
"Yes, we haven't had a settled back four, but everyone's played together before so I think that's just an excuse."
Knight is determined to help put things right in the final six games of the season as Villa look to secure European football.
"I don't know what the problem is. If I knew what it was, I'd be the manager wouldn't I?" Knight added.
"There are some very soft goals that we have let in. There have been times when we have been dropping off too deep and teams are getting a run at us.
"But we've got six games to put it right and we'll just have to sort it out for ourselves."