Sergio Aguero scored five times in 20 minutes as Manchester City came from behind to thrash Newcastle 6-1 and return to the Barclays Premier League summit.
Aleksandar Mitrovic had given the winless Magpies a shock lead at the Etihad Stadium but Aguero burst to life either side of half-time with a nine-minute hat-trick.
He bagged another pair before being substituted in the 66th minute, while the in-form Kevin De Bruyne was also on target as Newcastle went bottom.
Five-star perfomers
Sergio Aguero became the fifth player to score five goals in a single Premier League match. The others are:
Andy Cole
Cole became the first player to score five goals in the Premier League in the 9-0 humiliation of Ipswich at Old Trafford in March 1995.
Alan Shearer
Shearer netted a hat-trick in 12 first-half minutes and went on to grab two more as Newcastle hammered rock bottom Sheffield Wednesday at St James' Park in September 1999.
Dimitar Berbatov
Another individual five-goal feast for the Old Trafford fans as the Bulgarian bagged five in United's 7-1 thrashing of Blackburn in November 2010.
Jermain Defoe
Defoe stands alone in being the only player to score five goals in one half - scoring all five in the second 45 minutes of the 9-1 win over Wigan in 2009.
Chelsea capitulated and were booed off as Southampton won at Stamford Bridge for the first time in almost 14 years to leave Jose Mourinho contemplating a fourth loss from eight league games this season.
Captain John Terry was restored but Saints exposed the now familiar failings in the defence which just five months ago formed the foundation for winning the title.
Chelsea have conceded at least two goals in seven of their eight Premier League games this season - the exception the 2-0 defeat of Arsenal - and time and again Sadio Mane, Graziano Pelle and Dusan Tadic found holes in a 3-1 win.
Willian scored a fourth free-kick goal in four games to open the scoring, but Chelsea afterwards scarcely tested Maarten Stekelenburg as they fell to a first home loss to Saints since January 2002.
A rare Steven Davis goal levelled matters and Mane put the visitors ahead after mistakes by Gary Cahill and John Terry, before Pelle got Southampton's third.
Sunderland edged above their rivals with a 2-2 draw at home to West Ham but a first win of the season was let slip.
Steven Fletcher and Jeremain Lens put the Black Cats two up in 22 minutes, the latter with a lovely chipped finish.
But Carl Jenkinson pulled one back in first-half injury-time, Lens was sent off for a second yellow card and Dimitri Payet levelled on the hour.
Crystal Palace moved third in the table after a 2-0 home win in the early kick-off against West Brom.
It was 0-0 until the 68th minute, when Yannick Bolasie netted, and Yohan Cabaye's late penalty sealed it.
By then the Baggies had already lost Jonny Evans and James Morrison to injury.
Leicester, beaten by Arsenal last time out, returned to winning ways with a 2-1 success at Norwich.
Jamie Vardy won and converted a debatable penalty in the 28th minute, taking his tally to seven in eight appearances this season, before Jeffrey Schlupp doubled the lead.
Dieumerci Mbokani's first goal for the Canaries reduced the arrears but there was no equaliser.
A solitary strike from Marko Arnautovic saw Stoke take a 1-0 win at Aston Villa, who remain in the bottom three after failing to find a way past Jack Butland.
Arnautovic, who had earlier been denied by a marginal offside decision, beat Brad Guzan 10 minutes into the second half to hand the Potters a first away win since the same fixture in February.
Glenn Murray opened his Bournemouth account in the 1-1 draw against Watford at Dean Court, but missed a penalty to win it late on.
The Hornets were gifted their equaliser when goalkeeper Artur Boruc misplaced his kicked to striker Odion Ighalo.