The Blues' back-line got it all wrong at Blackburn, killing the momentum injected into their season off the back of three wins and a draw in five games.

Set-pieces were the key as Hart's team boobed on a harrowing hat-trick of occasions.

The man in charge explained eradicating those mistakes has been dealt with at the club's Eastleigh training base over the international break.

The loss at Ewood Park ensured his team remained adrift at the foot of the Premier League table after 12 games, with four points separating them from safety.

Those cold, hard facts are the vital statistics that count, of course, but are a long way from revealing the truth about the progress Pompey have made at the back before the Blackburn blip.

Four shut-outs came in the five-game period before the roof caved in against Sam Allardyce's men.

That was a world apart from the record-breaking nine Premier League defeats which opened the season, and had all and sundry condemning Pompey to the Championship.

Thirteen goals were shipped in that time, with five being conceded since then.

That stands up favourably when comparing Pompey's defensive record to those of their rivals.

Eight top-flight teams have conceded more goals than Hart's side so far this season.

Wolves, West Ham, Hull, Bolton, Blackburn, Wigan, Burnley and Sunderland have all let in more efforts than the Blues so far.

Liverpool's goals-against record is the same as Pompey's, while Spurs – who are sat in a Champions League place at present – have let in just one fewer.

Arsenal was the worst loss to date, a game they lost their way in during the second-half after William Gallas should have walked when he hauled down John Utaka. Hart's charges eventually lost 4-1.

Pompey have not suffered the kind of five and six-goal batterings dished out to Hull and Wigan, though.

Maybe things aren't so bad at the back after all.

It's individual defensive mistakes which have proved costly rather than wholesale chaos at the back.

A single player switching off at a critical moment or giving a striker that crucial yard has proved costly, rather than a sweeping lack of organisation.

That is something Hart has highlighted as cause for optimism, as well as the progress of his central defensive duo Marc Wilson and Younes Kaboul.

Despite their lack of years and relative shortage of Premier League experience compared to their peers, both men have shone after being thrown in at the deep end.

With an average age of 22-and-a-half they are comfortably the youngest central-defensive pairing in the top-flight, but have rarely been found wanting.

Steve Finnan's emergence after his hamstring horrors at the start of the season was another reason for the miserly air that Pompey found starting at Molineux against Wolves last month.

Hart's 'head it, kick it' mantra seemed to have seeped into the defence's consciousness after being incessantly preached.

Now, Pompey have to find that miserly touch all over again.

There are fewer places where they are going to find a sterner test of their defensive resilience than at the Britannia Stadium on Sunday.