Arsenal and Chelsea suffered damaging defeats on a night of upsets in the Champions League.
Arsenal's hopes of qualifying from Group F lie in tatters after a dismal 3-2 loss at home to Olympiacos.
The Greek side had lost on all 12 of their previous trips to England but made it lucky 13 as stand-in Gunners goalkeeper David Ospina had a night to forget.
Boss Arsene Wenger had warned his side already faced a must-win tie following their opening loss at Dinamo Zagreb but they fell behind after 32 minutes when a low shot from Felipe Pardo deflected off Alex Oxlade-Chamberlain.
Although Theo Walcott netted a quick equaliser, Arsenal found themselves trailing again when Ospina, chosen ahead of Petr Cech, dropped a corner over the line.
Alexis Sanchez levelled on 65 minutes, but Arsenal hit the self-destruct button once more as Olympiacos immediately scored through substitute Alfred Finnbogason.
Chelsea, who have made a poor start in their attempt to retain their Premier League title this season, crashed 2-1 at Jose Mourinho's former club Porto.
They fell beind when Yacine Brahimi waltzed inside Branislav Ivanovic and behind Pedro, then fired in a shot which keeper Asmir Begovic punched only as far as Felipe Andre Andre, who hooked the ball in.
Willian replied with a delightful curling free-kick on the stroke of half-time, but then woeful defending allowed Maicon to head in a corner seven minutes into the second half.
Diego Costa hit the crossbar, but Porto placed Chelsea under siege and the visitors were grateful to Begovic for some crucial saves while a Danilo header came off the post.
The shocks did not stop there with Italians Roma stunned 3-2 by Belarussian outsiders BATE Borisov.
The hosts raced into a 3-0 lead with just half an hour gone thanks to an early goal from Ihar Stasevich and Filip Mladenovic's double.
Gervinho and Vasilis Torosidis pulled goals back in the second half but BATE held on for a famous win.
Barcelona averted another upset with two late goals to come from behind and beat Bayer Leverkusen 2-1.
Kyriakos Papadopoulos headed the Germans into a 21st-minute lead and Barca, without talisman Lionel Messi through injury, struggled to get back into the game.
But Carnicer Sergi Roberto eventually equalised in the 81st minute and 90 seconds later Luis Suarez secured three points for the off-colour Catalan giants.
Less of a surprise was Robert Lewandowski being back among the goals, the striker taking his personal tally to 10 in three games with a hat-trick as Group F leaders Bayern Munich thumped Dinamo Zagreb 5-0.
In Chelsea's group, goals from Andriy Yarmolenko and Aluisio Junior Moraes gave Dynamo Kiev a 2-0 victory over Maccabi Tel-Aviv while in Group H, Valencia won 1-0 in Lyon and Zenit St Petersburg beat AA Gent 2-1.
