On Sunday West Ham beat Arsenal 2-0 at the Emirates.
Goalkeeper Petr Cech had an Arsenal league debut to forget as West Ham pulled off an unexpected 2-0 win at the Emirates Stadium.
The veteran Czech international moved from Chelsea in a £10million summer deal, which was seen as move to provide the Gunners with an edge in the Barclays Premier League title challenge.
However, Cech was caught out when West Ham midfielder Cheikhou Kouyate headed in a first-half free-kick and then Mauro Zarate slotted home a second on the break after 57 minutes to leave Gunners boss Arsene Wenger facing more questions about the direction of his side.
Chelsea were fortunate not to become the first ever Barclays Premier League champions to start their title defence with defeat after Swansea threatened an opening-day upset.
A celebratory atmosphere remained around Stamford Bridge as the club basked in the afterglow of last season's success - a feat Jose Mourinho, fresh from signing a new deal, warned would not be repeated unless they showed the "quality and determination of champions".
The Blues were found wanting in the first department against Garry Monk's impressive side, although they showed no little determination to secure a 2-2 draw after Thibaut Courtois' sending off.
Claudio Ranieri marked his return to the English top-flight in style as Leicester built on last season's stunning survival mission by thumping dismal Sunderland 4-2 at the King Power Stadium.
Ranieri, who replaced Nigel Pearson in the summer, watched Jamie Vardy head an early opener before a brace from Algerian Riyad Mahrez put the buoyant Foxes out of sight before half-time.
Mahrez, who signed a new deal at the club last week, missed two fine chances to complete his hat-trick before Jermain Defoe gave Sunderland a glimmer of hope by firing past Kasper Schmeichel.
Marc Albrighton put the seal on Leicester's win in the 66th minute and despite Steven Fletcher's late consolation it marked a worrying start to the season for Dick Advocaat's men.
Louis van Gaal's new-look Manchester United kicked off their campaign with an unconvincing 1-0 win over Tottenham in the lunchtime kick-off at Old Trafford.
Kyle Walker stabbed the ball into his own net to hand the points to the home side, who gave run-outs to five debutants including goalkeeper Sergio Romero.
Romero replaced regular number one David de Gea who watched from the stands after Van Gaal claimed he was not able to focus following interest from Real Madrid.
Memphis Depay, arguably the most impressive of the United new boys, played a key part in the counter-attack which led to Walker's unfortunate goal.
The Spurs man prodded the ball past his own keeper Michael Vorm in the 22nd minute after Depay and Ashley Young combined to set up a shooting chance for Wayne Rooney.
United had looked rusty up to that point with Christian Eriksen missing a good chance for Spurs, but Van Gaal's men held on to win a low-key opener with relative ease.
Watford fared best of the top-flight new boys after a flurry of late activity saw them earn a 2-2 draw against Everton at Goodison Park.
Miguel Layun's early opener looked set to snatch all three points for The Hornets as Romelu Lukaku and Arouna Kone missed golden chances to equalise for the home side.
Ross Barkley finally fired a long-range equaliser in the 76th minute and despite substitute Odion Ighalo putting Watford back in front seven minutes from time, Kone fired a second equaliser three minutes later.
But there was a harsh lesson for Eddie Howe's Bournemouth who dominated for long periods at home to Aston Villa before visiting substitute Rudy Gestede grabbed the only goal of the game in the 72nd minute.
The party mood was shattered at Goldsands Stadium when Gestede - signed for £6million from Blackburn last month - rose to head home an Ashley Westwood corner just 15 minutes after coming off the bench.
A late disallowed goal from Cameron Jerome denied Norwich the chance of a point as they slipped to a 3-1 defeat to Crystal Palace at Carrow Road.
Wilfried Zaha and Damien Delaney put the Eagles in charge before Nathan Redmond hauled the home side back into the game in the 66th minute.
Jerome thought he had levelled matters in the 70th minute but his overhead kick was controversially ruled out for dangerous play and Palace debutant Yohan Cabaye went on to confirm the visitors' win with a cool finish in injury time.