Jose Mourinho was humiliated on his return to Chelsea as his Manchester United defense was brutally exposed in a 4-0 loss Sunday by its ruthless hosts, who scored after only 30 seconds.

The Chelsea boss endured chants of "You're not special anymore" from home fans who adored the self-styled "Special One" when he was delivering titles across two spells in charge of the London club.

With Gary Cahill, Eden Hazard and N'Golo Kante also scoring after Pedro Rodriguez's lightning opener, this capitulation by United was reminiscent of the gloomy final days of Mourinho's second Chelsea reign which was abruptly halted last December with his firing.

United is quickly discovering the managerial aura which saw Mourinho win trophies with FC Porto, Chelsea, Real Madrid and Inter Milan will take a long way to being restored.

Counterpart Antonio Conte also had much to prove against Mourinho after losses to Liverpool and Chelsea in the opening weeks of his Chelsea reign. The Italian's players delivered before the first minute of the game had elapsed, setting the tone for a day of dominance.

The opener originated from a speculative long ball from Marcus Alonso which drifted past dithering defenders Daley Blind and Chris Smalling and landed at Pedro's feet. United goalkeeper David de Gea was already committed far from his goal-line at the edge of the penalty area and Pedro nipped around him and made no mistake putting the ball in the open net.

How United would then rue the miss by Zlatan Ibrahimovic who missed the target with a header. There was no way back for the record 20-time English champions, who have become a faded force since Alex Ferguson's retirement three years ago with David Moyes and then Louis van Gaal in charge.

It was another mistake by Smalling that allowed Chelsea to extend its lead in the 21st minute.

A Chelsea corner was flicked on at the near post by United's Antonio Valencia, then hit teammate Ander Herrera before the lethargic Smalling allowed Cahill to evade him and the Chelsea defender netted via Blind's back.

The game was becoming a reflection of the managers on the touchline. While Mourinho was subdued with his hands in his pocket, the energetic Conte was gesticulating enthusiastically.

And Conte was celebrating again just after the hour.

Eden Hazard started the incisive move that ended with a third goal. N'Golo Kante then squared to Nemanja Matic, who returned the ball for Hazard to turn Smalling before dispatching the ball into the corner of the net.

There was worse to come for Mourinho. Pedro, who started the rout, set up Kante to complete it. Kante waltzed through United's brittle defense with ease, going past Smalling — who else? — before slotting beyond De Gea.

Manchester City failed to win for a fifth successive game in all competitions on Sunday, only avoiding a loss to Southampton when Kelechi Iheanacho produced a second-half equalizer.

Although Pep Guardiola is enduring a five-game winless run for the first time since his debut campaign in charge of Barcelona in 2008-09, City is top of the Premier League on goal difference.

A mistake by City defender John Stones presented Nathan Redmond with the opener in the 27th minute at home. Substitute Iheanacho equalized 10 minutes into the second half with City's first shot on target but the hosts could not find the winner.

City could feel hard done by after dominating possession, particularly in the second half, and having a Stones goal ruled out for offside. Yet after opening the season with 10 successive wins, the intensity does seem to have dropped temporarily.

After Wednesday's loss at Barcelona in the Champions League, City's players needed to make a statement in response but they could not rouse themselves enough after a subdued first-half performance.

Sergio Aguero was restored to the front line after his surprise omission at Barcelona, while fit-again captain Vincent Kompany made his first league start since April.

City struggled to get going, with promising runs from Aguero, Raheem Sterling and Leroy Sane all coming to nothing. City's lack of cutting edge suited Southampton, who struggled to gain any meaningful possession.

When Southampton took the lead it came after a glaring error by Stones, who did not look up as he passed the ball back into the area in the 27th minute. Kompany was not in tune with his fellow defender and Redmond pounced, taking the ball wide of goalkeeper Claudio Bravo and scoring.

The look on Stones' face made clear the horror of his error, which will bring into further focus Guardiola's determination to play out from the back at seemingly all costs.

Stones picked himself up and thought he had made quick amends as he raced in at the far post to tuck home a De Bruyne free-kick. He celebrated what he assumed was the equaliser with gusto but a flag had been raised for what appeared to be offside against Aguero.

The frustration continued for City as Ilkay Gundogan drove wide but the introduction of Iheanacho at halftime brought a change in shape, intensity and atmosphere.

Sterling was enlivened and curled a dangerous ball through the box before City claimed their equalizer. Fernandinho picked out Sane with an accurate crossfield ball and his low cross was neatly tucked in by Iheanacho.

From then on it mainly became a case of Southampton digging in and looking to protect what they had, although Bravo was called upon to make one save from a Charlie Austin drive. Goalkeeper Fraser Forster kept Southampton level by palming away Gundogan's effort before saving David Silva's long-range strike to secure the point for the south-coast side, which is eighth in the standings.