HARRY REDKNAPP laid the blame squarely on defensive errors as Saints surrendered a two goal lead in hugely disappointing fashion.
The Saints boss said there was a lack of pace and communication among the back four, pinpointing the half-time loss of Andreas Jakobsson as a turning point in the game.
Although they had rode their luck on occasions, Saints went in 2-0 ahead at the interval, only to lose Jakobsson with a hip injury.
He was replaced by Calum Davenport while Aston Villa brought on Carlton Cole and Nolberto Solano.
"I lost Jakobsson at half-time and that was a big turning point," said Redknapp.
"We didn't get near Solano and we let Cole bully us, that was the problem.
"The back four just couldn't defend. They dropped deeper and deeper and couldn't defend.
"We've got a back four with no talkers at the back. We get under pressure and we drop deeper and deeper. We lack pace so we drop deeper and it invites pressure.
"We've got no pace at the back. It's a team with no quick defenders."
Villa's goals came in a dreadful 17 minute second-half spell through Carlton Cole, Nolberto Solano and Steve Davis.
Redknapp's current first-choice centre-back partnership is Claus Lundekvam and Jakobsson, although he did previously play Davenport.
Other options are Danny Higginbotham or he could even take England under-19 skipper Martin Cranie out of Saints' FA Youth Cup final team and draft him into the squad to face Bolton.
Jason Dodd and Darren Kenton are both currently out on loan.
"I've not got an awful lot to bring in," said Redknapp. "I can't say 'I've got this one and that one at the back', I'm short there."
The Saints boss could take some heart from a strong first-half display and good performances from the likes of Kevin Phillips, Jamie Redknapp, Nigel Quashie, Paul Telfer and Peter Crouch.
"We were absolutely fantastic in the first-half, we were great in the middle of the park and up-front fantastic," said Redknapp.
"The first-half was a fantastic performances and there were positives.
"All the negatives were at the back. There was no other negative.
"You shouldn't have to get three goals to win a game at home. There's got to be something wrong.
"Defensively we were not strong enough. We stood off them and let them play."
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