West Bromwich Albion inflicted further misery on Manchester United, winning 2-1 at Old Trafford on Saturday to condemn the champions to their worst start to a Premier League season and leave them in the bottom half of the table after six games.
Morgan Amalfitano and Saido Berahino scored for the visitors either side of a Wayne Rooney leveller to leave United in 12th place in the table a week after they suffered a crushing defeat to local rivals Manchester City.
City also suffered a surprise defeat at Aston Villa, who scored three second-half goals to win 3-2 at Villa Park, leaving Tottenham Hotspur top of the table after a 1-1 draw with Chelsea earlier on Saturday.
John Terry headed a second-half equaliser for Chelsea as the managerial battle between Jose Mourinho and his former apprentice Andre Villas-Boas ended in stalemate.
Southampton's watertight defence held firm as they climbed to fourth with a 2-0 win at home to Crystal Palace, Hull City won 1-0 against West Ham United and Cardiff City won 2-1 away at struggling Fulham.
Arsenal can return to the summit if they beat Swansea City in Saturday's late kickoff.
Superb Mata wins over Mourinho
Juan Mata won over coach Jose Mourinho after coming on as a halftime substitute to galvanise Chelsea to a 1-1 draw at Tottenham Hotspur.
The Spain international has been in and out of the side under Mourinho this season with the Portuguese boss publicly stating that Brazilian Oscar has been his preferred choice in the playmaker's No.10 role.
Mata injected some impetus into Chelsea on Saturday though and Mourinho said he was so impressed by his attitude and recent performances he would definitely start against Steaua Bucharest in the Champions League on Tuesday.
"He is coming further towards what I want," Mourinho said. "I think this is the way players have to say 'I want to play.'
"'Blah blah blah is not good. Conversations with you are not good. Good is the effort he made against Swindon and the way he changed the team in the second half today.
"And because of that I am very happy to say that 72 hours in advance, he will play against Steaua Bucharest.
"He won that by himself."
Image: Manchester United players react after a West Bromwich Albion goal during their English Premier League match at Old Trafford.
Photo: REUTERS/Phil Noble