Chelsea suffered their first home defeat in the Champions League group stage for ten years as Basel caused a major upset, while Arsenal recorded a valuable victory in Marseille and Lionel Messi starred again for Barcelona.
• Cross: Ramsey performance epitomises Arsenal
• Palmer: Lessons taken from Arsenal win
• Delaney: Chelsea issues exposed in Basel loss
• Tomas: Barcelona blast four goals past Ajax
• Paul: Depleted Milan secure vital three points
Jose Mourinho’s inauspicious start to his second Chelsea spell continued as the Blues crashed to a shock 2-1 home defeat to FC Basel in their Champions League opener.
Oscar gave Chelsea the lead in the first half but Basel rallied and goals from Mohamed Salah and Marco Streller handed the Swiss side a famous victory in West London.
It was the Blues’ second defeat in a row following a Premier League loss at Everton and their first at home in the Champions League since Manchester United’s quarter-final victory in 2011.
Wednesday’s other Group E encounter saw Schalke dominate Steaua Bucuresti, beating the Romanian champions 3-0 at the Veltins Arena thanks to goals from Atsuto Uchida, Kevin-Prince Boateng and Julian Draxler.
In Group F, Arsenal recorded a record tenth straight away win in all competitions as strikes from Theo Walcott and in-form Aaron Ramsey secured a valuable 2-1 victory in Marseille.
Walcott volleyed home the Gunners’ opener before Ramsey scored his sixth goal in seven games this season, a stat made all the more remarkable considering he netted just two in 47 last season. Jordan Ayew converted a late spot-kick but it was too little, too late for Marseille.
Napoli also claimed a 2-1 win, as they held on to beat ten-man Borussia Dortmund at the Stadio San Paolo.
Last season's losing finalists Dortmund endured a horror start to the new campaign on a stormy night in souther Italy. Gonzalo Higuain and Lorenzo Insigne put Napoli 2-0 up and they got the points despite a Camilo Zuniga own goal, but the red mist which descended on Jurgen Klopp and some of his players were the real story.
Klopp is known for his cool demeanour, but he was positively raging as he towered over the fourth official, barking at him relentlessly, in the wake of Higuian's goal.
He was unhappy that Neven Subotic had been allowed back on after treatment but not in time to prevent the goal. Klopp was dismissed to the stands and on the stroke of half-time was joined by goalkeeper Roman Weidenfeller who raced out of his box to try and close down Higuain but handled in front of the referee.
Lionel Messi moved closer to Raul’s Champions League scoring record with a hat-trick in Barcelona’s impressive 4-0 Group H victory over Dutch champions Ajax.
Messi is now just nine goals behind the Real Madrid legend’s haul of 71 goals after emulating Cristiano Ronaldo’s Tuesday treble with three of his own at Camp Nou.
Gerard Pique was also on the scoresheet as Gerardo Martino’s side cruised to an opening win that was damaging to the confidence, and goal difference, of Frank De Boer’s Ajax.
Elsewhere in Group H, Celtic produced a rousing European display away to AC Milan but were beaten 2-0 thanks to a late own goal by Emilio Izaguirre and a further effort from Sulley Muntari.
The Hoops, who beat Barcelona in last season’s group stage, were resolute at the San Siro, but eventually came undone as the Rossoneri got a huge slice of luck when defender Cristian Zapata's drive in the 82nd minute appeared to be heading wide before it deflected off Celtic left-back Izaguirre and ended up behind Fraser Forster.
The Celtic goalkeeper was beaten again four minutes later despite making a great save from Mario Balotelli's free-kick, as midfielder Sulley Muntari knocked in the rebound.
Lucho Gonzalez scored the only goal of the night as Porto ensured Austria Vienna's debut in the Champions League group stage ended in a narrow 1-0 defeat.
Gonzalez found the target 10 minutes into the second half as Porto made the perfect start to their European campaign. Hosts Vienna had their moments at the Ernst Happel Stadium, with Marko Stankovic unlucky to see his second-half header hit the post, but better will be needed if they are to avoid becoming also-rans in Group G.
Atletico Madrid got their European season off to a strong start by producing a thorough performance to beat Zenit St Petersburg 3-1 at the Vicente Calderon.
Joao Miranda's headed goal had given the hosts the lead towards the end of the first half, but a stunning effort from Hulk drew the Russian side level.
Arda Turan restored Atletico's lead not long after the equaliser, and then substitute Leo Baptistao scored his first competitive goal for the Rojiblancos to seal the win. The most high-profile absentee from Atletico's starting line-up was Diego Costa, who was suspended after being sent off against Viktoria Plzen in last season's Europa League, and Adrian Lopez started in his place in attack, alongside David Villa.