Clark Robertson responds to Portsmouth critics after worrying defensive performances against Plymouth, Ipswich and Charlton

However, the Blues skipper admits they do have the right characters in the backline to sort out their concerning issues.

Following Joe Rafferty’s spell on the sidelines with a stomach injury, Connor Ogilvie has been moved to right-back while Clark Robertson filled in on the left.

Despite picking up a win in their first game as a makeshift back four, the defence has come under heavy fire in recent weeks after worrying displays against Ipswich, Plymouth and Fleetwood.

This saw the Fratton faithful call on Danny Cowley to bring Zak Swanson or Kieran Freeman into the side with Ogilvie reverting to his left-back role.

Indeed, the head coach’s team selection came into question once again for Pompey’s trip to Charlton on Monday evening as he stuck with the same four defenders for the tie.

Robertson though admits the Blues’ new defence has worked and have made the best out of a bad injury situation.

He told The News: ‘It’s difficult, we’ve obviously had a few boys playing out of position. It has worked out up until now, I think in games it has worked.

‘Obviously we’ve had a few injuries and it’s just been one of those things.

‘It was a very bad night for us defensively though but it is only us that can change that.

‘We’ve got to work hard on the training pitch, we’ve got to be even stronger and much more streetwise.

‘We lost the battle tonight and if you don't win that, you won’t be able to show your quality because we do have quality in the squad but we’re conceding soft goals.

‘We’ve got good experience in this team and great characters in the defence and it’s up to us to fix that for Saturday.’

Further fingers were pointed at the backline following their 3-0 thrashing by Charlton, with two of the three goals coming from set-pieces.

Robertson has called on the defence to do more and insists drastic improvements are needed.He added: ‘We’ve been working on the training pitch but we’re going to have to do more because that was far from good enough.

‘If you don’t defend in the box and don’t attack balls in set-pieces then you’re going to be in trouble.

‘Set-pieces are vital in football and we need to sort that out quickly because it's becoming a big issue.’