Sam Allardyce goes back to the drawing board after seeing his worst nightmares become painful reality.

The 52-year-old arrived at St James' Park determined once and for all to rid the club of their reputation for defensive fragility and instil within his new-look squad the capacity to win ugly.

Indeed, Allardyce invested the best part of £14million in defensive reinforcements this summer in an effort to finally eradicate the errors which had proved so costly over the previous decade or more.

Claudio Cacapa, Abdoulaye Faye, Habib Beye, David Rozehnal and Jose Enrique were all recruited as the new manager's brave new world took shape.

But in the space of 180 minutes - or more accurately, 101 minutes - of football at Reading last weekend and then at home to Portsmouth seven days later, all the hard work unravelled in spectacular fashion.

If Allardyce had bristled at his side's capitulation at the Madejski Stadium, he was horrified to see his rearguard implode on their own park to hand impressive Pompey a comprehensive victory.

The shell-shocked Magpies now face a trip to derby rivals Sunderland on Saturday for a game they dare not lose with confidence in short supply and their defence yet again under the spotlight for the wrong reasons.

Allardyce said: "The basic errors from the back four have to be cut out.

"We are working in all areas during the week and trying to get the players to understand how the Premier League can hurt you unless you stay together as a unit.

"The biggest unit of all has to be the back four, knowing how each other play and understanding each other.

"But after all that, I cannot cut out basic errors. If it's great play and intricate play and the opposition play around you and through you, you have to hold your hands up sometimes if your defenders have been trying to do the right thing.

"But when it boils down to two basic errors like it did, then there's very little as a manager you can do.

"But you have to keep working and hope it does not knock their confidence too much and keep showing them what solid, good, organised defensive work looks like in the Premier League."

No amount of hard work and organisation would have prevented Noe Pamarot's opener, a 25-yard thunderbolt which screamed past stand-in goalkeeper Steve Harper on eight minutes with little prospect of him getting anywhere near it.

But within three more barely believable minutes, Pompey were out of sight, and on both occasions, the finger was pointed at Cacapa.

The Brazilian, who helped provide the foundation for much of Lyon's success during his time in France, has looked accomplished in his games at St James' Park so far this season.

But in a disastrous 16-minute spell before he was hauled off, he was out-manoeuvred and out-muscled, first by Benjani Mwaruwari and then John Utaka, as the visitors gleefully accepted gift-wrapped chances.

If Cacapa was the villain in chief, he was not alone as Newcastle's laboured response briefly gave them hope with Sol Campbell putting through his own goal on 15 minutes.

But Pompey should have had a penalty for a clear handball by Cacapa's replacement Rozehnal, and Niko Kranjcar's 70th-minute free-kick, which might have been cut out by Steven Taylor, Faye and Harper, was the final straw.

Perhaps more worrying for the Newcastle faithful, many of whom trudged away long before the final whistle, was their side's lack of creativity on an afternoon when Sulley Muntari, Utaka, Benjani and Kranjcar simply had too much craft, guile and pace for the men in black and white.

Allardyce had to shoulder his share of the blame - he failed to abandon his ploy of fielding left-winger Charles N'Zogbia on the right and the right-sided James Milner on the left when it patently was not working, starving Michael Owen and Alan Smith of meaningful possession.

Allardyce said: "By no stretch of the imagination is it just the defence. It is the protection from the balls into the back four and the quality of balls the opposition can play without any pressure on them.

"Defending starts from the front, not from the back. But I do not think that, in the first 12 minutes, was the case, it came about because of basic errors.

"From then on, life was very difficult for us."

But if Allardyce was left licking his wounds, opposite number Harry Redknapp was hoping his side's development - it was their fourth successive league win away from home and their first on Tyneside in 58 years - has gone unnoticed.

He said: "I hope we can just keep going away from home picking up results like we have recently.

"But we are a big, strong, imposing team with ability and a bit of pace."

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