Everton crumbled for the second time in four days as their disastrous season continued with a chastening defeat at Southampton. The travelling supporters could have been forgiven for thinking it could not get any worse but this inept display, lacking resolve or fight, was damning evidence that Everton really are a sorry mess. Their lofty ambitions this season have long since evaporated and David Unsworth must be in a minority in thinking they are not in a relegation battle.

Everton, without a clean sheet since the opening day, were again a defensive shambles and after shipping another four goals here have conceded nine in two outings. They were pulled apart, with Steven Davis completing the rout after Dusan Tadic’s opener and a Charlie Austin double. By the end Gylfi Sigurdsson’s spectacular first-half equaliser was a distant memory and the prospect of relegation an ever-increasing reality, with the club two points above the bottom three.

The manager who inherits this from the caretaker Unsworth will have quite a job on his hands; this is a fifth defeat in seven matches since Ronald Koeman’s sacking. Asked whether Everton were in a relegation battle, Unsworth replied: “I wouldn’t go that far so early. I think we are in a tough moment, and I think we have a massive week ahead of us. Our confidence is very, very low and we are conceding far too easily. The players know that and, if they didn’t know they were in a tough situation, then they must do now. It’s a massive week for the club.”

The upcoming seven days comprise what look like must-win matches against West Ham United and Huddersfield Town at Goodison Park. “It is not good enough and it has to change,” Unsworth said. “Something has to change because this group of players is underperforming. Whether it’s Ronald in charge or myself in charge, it’s not working.”

Everton were slapdash in possession and shirked challenges, with most passes aimless and too many players seemingly uninterested. This was the meekest attempt to put right the wrongs of Thursday’s 5-1 capitulation at the hands of Atalanta and left Unsworth, a staunch club servant, grimacing. For Mauricio Pellegrino, who has compared managing Southampton to going to the gym because hard work has not provided instant results, this domineering and confident showing was evidence of significant progress.

“The first half we played really well but after they equalised the team was patient and we continued playing in the same way,” Pellegrino said. “After we scored the third one it was easy for us because we had the space and we created a lot of chances.”

It was a breeze for Southampton, who badly needed some light relief after an indifferent start to the season. Pellegrino tweaked personnel, handing Austin his first league start, as Southampton sought a third home win. Unsworth, meanwhile, made eight changes from the team thumped by Atalanta, including dropping Wayne Rooney who remained on the bench. But 72 hours on it was the same old story with this Everton display equally torturous viewing.

The only surprise when Everton fell behind after 18 minutes was that it had taken so long. Austin had stabbed wide and struck the woodwork before Tadic rounded off a superb sweeping team move. His deft finish trickled through the legs of Jordan Pickford, the Everton goalkeeper, who was horribly exposed time and again, after racing on to Ryan Bertrand’s slide-rule pass. Pickford erupted, angered at the gaping hole between Michael Keane and Leighton Baines, who was then replaced by Ashley Williams owing to a calf injury. As another chance flew past Pickford’s post, a smattering of boos rang out from a pocket of fans in the away end.

In fairness few could have foreseen Everton’s next move. With the interval fast approaching, Sigurdsson picked up the ball 25 yards from goal, with seemingly no danger to Southampton until he jinked inside on to his right foot, fooling Davis and Virgil van Dijk. He then wrapped his boot round the ball and sent a crashing effort goalwards, which pinballed between the bar, post and bar again before falling into the cushion of the side netting.

Fortunately for Southampton, Everton quickly returned to their bad habits after half-time. More slack defending allowed Bertrand to ghost in down the left and again turn supplier, this time to feed Austin at the near post, with the striker comfortably beating Keane and Williams in the challenge to thunder his header in off the bar.

Five minutes later it was déjà vu; with Everton’s defence again at sea, an unmarked Austin powered home beyond a hapless Pickford from Tadic’s cross. Southampton almost added another through the substitute Shane Long but Pickford saved after the striker wriggled free of Phil Jagielka. Saints did, though, find a fourth when Davis fired in low two minutes from time. Unsworth’s tired shake of the head at full time said it all.