Frank Lampard walked to a quiet part of the pitch, alone, then headed for sanctuary, shaking his head in the slow, rhythmic way of one who knows the good times have receded. They will be back, certainly, for one of the best English midfielders since 1966, but on this day he drew a blank again and made a defensive error that started Chelsea's slide.

Two consecutive away defeats in the Premier League have stirred the ghost of Luiz Felipe Scolari. Chelsea have now been beaten at Wigan and Aston Villa in nine league outings. The curse of vulnerability at set plays has returned. To call it a crisis, or even an emergency, would be an abuse of the English language. But both Villa's goals stemmed from defensive aberrations and Lampard's only influence on the scoreboard was at the wrong end.

News of a Lampard goal at club level can be kept on a default key, especially late in games, when the joint heart of this Chelsea side is adept at rescuing Roman Abramovich's investment. This season, though, he has not located the net since the 3-1 win over Sunderland way back on 18 August. In Chelsea's top scorers' list he is outgunned by the left-back Ashley Cole. This from a marauding midfielder who has scored 108 times in his days at Stamford Bridge and can realistically aim to farm 20 or so in each campaign.

Maybe it was just the first-half mistake at a Villa corner taken by Ashley Young that rendered him so desolate as he left the field. In the first defensive position, in a line just outside the near post, Lampard got underneath Young's delivery and allowed it to skim off his head into the Chelsea penalty area. There to greet the ball was Richard Dunne, who dived at it like a man jumping through a hoop.

Chelsea's lead, through a Didier Drogba drive that bounced over a horizontal Brad Friedel, was wiped out, but the rear of Carlo Ancelotti's side were only warming up for an even worse mistake. After the break, Young swung in another corner, this time to the far post, and Dunne's fellow centre-back, James Collins, arrived unchallenged to win the game for Villa.

Scolari's regime unravelled because he failed to preserve the team's great organisational strength and thought it could be replaced overnight by fluidity and self-expression. Ancelotti cannot pick up the tab for Lampard's howler or the inability of John Terry and Ricardo Carvalho to deal with one of Wales's centre-halves in their own penalty area. There is, though, a sharp need for the Italian coach to correct these letdowns before they become a pattern. The Wigan result could be chalked off as a freak. This latest misfortune, against a resolute, enterprising Villa side, invites every other Premier League side through the door that two non-top four clubs have smashed open.

Ancelotti was morose afterwards, but Martin O'Neill, the Villa manager, rode to his assistance with a real paean to his victims. "I think they [Terry and Carvalho] are brilliant players, and they've proved that over five or six years," O'Neill said. "I wouldn't try to draw 15 conclusions from today. They are a really top-quality side. I'm delighted with our two boys [Dunne and Collins]. It sounds sycophantic, but I think Chelsea are brilliant.

"I think they can play. They're never given credit for the way they can play and move it. I'll take another look at the 20 minutes when they were playing straight through us. Chelsea do that every week. If you have any aspirations you will want to be like Chelsea."

This view has many knowledgeable adherents. Yet Chelsea are developing a problem beyond the return of set-piece shakiness. Lampard, the team's chief dynamic force, has temporarily lost the sheen that goes with that job – more, even, than when Michael Ballack was getting in his way. The suspicion is that Ancelotti has not yet understood the primary truth of his team's forward play. When Lampard is the driver, Chelsea get where they need to go.

His club career used to be one long pomp, while England fans asked why he never played that well for his country. The tables have turned a bit this autumn. With his 76 caps, Lampard is now a proven international orchestrator but has lost impetus at his club. Against Villa here he played on the right side of a midfield diamond, with Deco in the centre. However Ancelotti might explain that, it meant that Lampard was subservient to a fringe player. Only in the last 20 minutes, when Chelsea were chasing the game, did the superior player probe left, right and centre, in his old, free role.

Simply, Lampard was too wide and too deep too often to exert full influence on the match. Ancelotti, rather coldly, has spoken of the player's "need" to adapt. But he should know his No8 is capable of brooding. Milan's former coach needs no lectures on the art of midfield play, but the disruption to Lampard's goalscoring form points to Abramovich's folly in constantly changing the Chelsea manager. Guus Hiddink, last season's caretaker, was much quicker to understand Lampard's value.

"I'm not interested in whether he scores, I'm interested in whether he works for the team, and he works very hard," Ancelotti said. But Lampard is not just a labourer. He is Chelsea's senior game-changer, and they need him to be scoring again.