London: Liverpool suffered a surprise 3-1 loss away to West Ham on Saturday as fresh questions were raised about whether they have the defence required to win the Premier League title.
Brendan Rodgers's side were 2-0 down inside seven minutes at Upton Park.
Poor defending by Liverpool -- who've now lost three of their five league games this season -- saw the visitors fail to deal with James Tomkins's knock down and Winston Reid turned the ball in to put the Hammers 1-0 up in the second minute.
And the London side doubled their lead minutes later when Senegal forward Diafra Sakho's intended cross beat everyone, including Liverpool goalkeeper Simon Mignolet.
Defensive errors cost Liverpool the title when they finished runners-up to champions Manchester City last term.
But they remain a potent attacking force and England winger Raheem Sterling pulled a goal back with an unstoppable shot from inside the box in the 26th minute after Mario Balotelli's initial effort was blocked.
However, substitute Morgan Amalfitano made the game safe for Sam Allardyce's West Ham side two minutes from time when he latched on to former Liverpool winger Stewart Downing's through-ball before finding the far corner.
Earlier, Arsenal stopped Aston Villa going top of the table courtesy of a 3-0 win, with the much-criticised Mesut Ozil on target.
Villa had conceded just one league goal in their previous four league matches but all that changed as Arsenal fired in three inside four minutes at Villa Park.
Ozil put the Gunners in front in the 32nd minute and former Manchester United striker Danny Welbeck scored his first Arsenal goal two minutes later before Villa's Aly Cissokho turned the ball into his own net.
Meanwhile Newcastle moved off the bottom of the table and eased the pressure on manager Alan Pardew by coming from 2-0 down to draw 2-2 at home to Hull, with substitute Papiss Cisse scoring both the Magpies' goals inside the final 15 minutes.
Southampton went second with a 1-0 away to a Swansea side who had to play more than half the match a man down after Ivory Coast striker Wilfried Bony was sent off.
QPR and Stoke shared the points in a 2-2 draw at Loftus Road while honours were also even in the goalless stalemate between Burnley and Sunderland.
Arsenal manager Arsene Wenger had been forced to again defend Germany World Cup-winner Ozil, a club record £42 million ($76 million) signing from Real Madrid last term, after his uninspiring display in the Gunners' 2-0 Champions League defeat at Borussia Dortmund in midweek.
But, played in by Welbeck, he made no mistake with a side-foot chance to put Arsenal ahead on Saturday.
Minutes later, the roles were reversed when Ozil's cross found Welbeck, whose shot found the roof of the net.
Kieran Gibbs's cross-shot was then turned into his own net by Cissokho.
Arsenal moved to within a point of second-placed Villa and three adrift of leaders Chelsea.
Wenger confidence in Ozil
"I never considered leaving Ozil out," said Wenger. "He showed as well he can perform when under scrutiny."
Villa were hit with a sickness bug before kick-off and manager Paul Lambert said: "To play Arsenal you need everyone fit...I don't know what kind of virus it is but it is certainly doing its job."
Nikica Jelavic put visitors Hull ahead with an acrobatic effort from 15 yards out early in the second half before Senegal midfielder Mohamed Diame doubled the lead in the 68th minute with a brilliant 25-yard shot.
But then came Cisse's rescue act.
"I am very proud to be manager of this club and I will fight to keep it," said Pardew.
At Swansea, Bony was shown a red card in the 39th minute when he took away the legs of Maya Yoshida -- his second bookable offence.
But it took until 10 minutes before time for Southampton to make their numerical advantage count thanks to substitute Victor Wanyama's first goal for the Saints.
Croatia's Niko Kranjcar salvaged a draw for QPR with a goal two minutes from time at Loftus Road.
Mame Biram Diouf opened the scoring for visitors Stoke. Steven Caulker equalised before Peter Crouch restored Stoke's lead against his former club.
Sunday sees Chelsea looking to maintain their perfect league record this season away to Manchester City.
Manchester United will go in search of their first away league win under manager Louis van Gaal, at Leicester, while Tottenham Hotspur take on West Bromwich Albion and Everton face Crystal Palace.