Premier League leaders Liverpool crashed to their first defeat of the season at home to Southampton on Saturday, while Everton enjoyed a stirring 3-2 win against West Ham United.
Liverpool were without injured playmaker Philippe Coutinho, sidelined by a shoulder problem, but they came close to taking the lead in the first half at Anfield when visiting goalkeeper Artur Boruc produced a full-stretch save to keep out a Steven Gerrard free-kick.
Daniel Sturridge then had a penalty appeal turned down after tangling with Dejan Lovren, and it was Lovren who broke the deadlock in the 53rd minute with a back-post header from a left-wing corner.
Only a fine triple save from Simon Mignolet prevented Southampton from adding to their lead, but Lovren’s goal proved enough to inflict a first league defeat on Liverpool since a 3-1 loss to the same side last March.
Liverpool will lose their grip on first place if Chelsea win at home to Fulham later on Saturday, while Everton now trail their city rivals by only a point after Romelu Lukaku scored on his debut to settle a thrilling game at Upton Park and help preserve the last unbeaten record in the division.
West Ham twice took the lead, via a deflected shot from Ravel Morrison and a Mark Noble penalty, only for Leighton Baines to level on each occasion with a pair of sensational free-kicks from 25 yards.
Noble was then sent off for a foul on Ross Barkley before Lukaku headed home an 85th-minute winner in his first game since being loaned from Chelsea.
Earlier, Aston Villa lost key striker Christian Benteke to injury but still managed to snap a three-game losing streak with a 1-0 win at Norwich City.
Last season’s top scorer with 19 goals, Benteke limped off with an injury during the first half but his replacement, Libor Kozak, tapped in the game’s only goal within two minutes of coming on.
Villa manager Lambert played down Benteke’s injury, saying: “The medical staff reckon it’s his hip flexor. Hopefully it’s not too bad.”
Manchester United visit Manchester City on Sunday in the season’s first Manchester derby, when both City manager Manuel Pellegrini and his United counterpart David Moyes will be sampling the fixture for the first time.