Southampton badly needed to beat mid-table Villa and were given the perfect start when they went two goals ahead after only 13 minutes.
Saints were ahead after only four minutes when Peter Crouch got away down the right and crossed for Kevin Phillips to score from 12 yards.
Southampton went further in front in the 13th minute when Jamie Redknapp was allowed to run from the halfway line to set up an easy goal for former Villa striker Crouch.
There might have been more goals for Harry Redknapp's side but Villa goalkeeper Thomas Sorensen made two excellent saves before the break.
The match was turned on its head when Nolberto Solano came on as a half-time substitute and, within ten minutes he had set up a goal for another substitute, Carlton Cole.
Solano equalised in the 70th minute and, with Southampton now in disarray, Stephen Davis added a third.
Cole, who had replaced the injured Darius Vassell in the 36th minute, broke clear only to shot into the side-netting as Villa went in search of a fourth.
Southampton threw players forward in a desperate bid to snatch an equaliser and Henri Camara shot wide when well-placed, hanging his head in shame and disappointment at the near miss.
Harry Redknapp left his seat on the bench in the closing stages to pace up and down his technical area with increasing nervousness but nothing worked.
Crouch, who capped a dominant first-half performance with his 14th goal of the season against his old club, was an isolated figure for much of the second half.
His strike partner Phillips, a target for Villa in the January transfer window, was also starved of opportunities after a bright first half.
Villa, without ever hitting top form, had been allowed to get back into a match that seemed to have slipped from their grasp long before the break.
MAN OF THE MATCH: Nolberto Solano (Aston Villa) - Came on at the interval as a substitute and transformed the match by making one goal and scoring another. The Peruvian's efforts ensured the match really was a game of two halves.