Zat Knight admits Aston Villa's defending hasn't been good enough since the turn of the year.

The centre-half told the Press Association: "It's frustrating what has been happening - especially as a defender. Your main aim as a defender is to go out there and keep a clean sheet and if 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. I don't know what the problem is. If I knew what it was, I'd be the manager wouldn't I?

"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."