Schalke 04 became the first non-English team to win a European game at Arsenal in nine years as Klaas-Jan Huntelaar and Ibrahim Afellay clinched a 2-0 victory to put the Germans top of Champions League Group B today.
Arsenal had not lost at home to foreign opposition since 2003 when Inter Milan claimed the points but their Emirates Stadium fortress looked anything but secure as they produced a woeful performance, managing just one effort on target.
They still looked like escaping with a 0-0 draw as Schalke, riding high in the Bundesliga after beating arch-rivals Borussia Dortmund at the weekend, wasted some great opportunities but Arsenal's luck finally ran out.
Dutchman Huntelaar rifled a shot past keeper Vito Mannone with 14 minutes remaining to give the Germans a deserved lead and Afellay, on loan from Barcelona, sent the boisterous away fans into party-mode with a tap-in second in the 86th minute.
Arsenal's disgruntled fans had already started heading for the exits and unless their team rediscover some form, what appeared to be a relatively easy passage to the last 16 may still become problematic with a trip to Gelsenkirchen next up on Nov. 6.
The north London side have six points, one behind Schalke who look well-placed to take top spot with three games left.
"We seem to be lacking a bit of confidence with the ball," Arsenal's assistant manager Steve Bould, who was in charge as Arsene Wenger sat out the third and final game of a European touchline ban, told reporters.
"They are a really good side and it's a tough competition. A 0-0 would have delighted us.
"We've still got nine points to play for and I'm sure we'll perform a damn sight better next time."
Schalke boss Huub Stevens felt his side had been deserved winners.
"I was not happy with the first half, we were too cagey," he said. "We are happy with seven points, we have won two games in a row but there is a long way to go.
"In the second half we deserved to win the game. Huntelaar is Huntelaar, if he is in the box and you let him go he will get his goal."
"Arsenal are still the favourites for the group when they get some of their players back."
Arsenal did start reasonably brightly with Gervinho nearly getting a foot to a Lukas Podolski cross but the home side's confidence, rocked by a 1-0 defeat by Norwich City at the weekend, quickly drained away.
In his programme notes, Wenger described his side as having had "illusory possession" at Norwich and they again flattered to deceive in a sterile first half.
Missing the pace of the injured Theo Walcott and Alex Oxlade-Chamberlain and with Santi Cazorla struggling to impose himself in midfield, the home side hardly tested visiting keeper Lars Unnerstall before the interval.
When Schalke finally began to throw off the shackles they were by far the more threatening side.
They were unlucky not to have been awarded a penalty after 14 minutes when Afellay appeared to have his ankles clipped by Mannone as he raced into the area.
Much to the disgust of Stevens, Afellay received a yellow card for diving - a fate that also awaited Gervinho late on for a much more blatant tumble to the turf.
Peruvian Jefferson Farfan twice elected to pass rather than shoot and moments before the interval Huntelaar wasted a golden opportunity, shooting hopelessly wide of a yawning goal when set up by Atsuto Uchida's low cross.
Kicking towards their fans Schalke began the second half brightly but were guilty of more profligate finishing when Farfan cut a low pass back to captain Benedikt Hoewedes inside the penalty area but he scooped his shot over the crossbar.
Arsenal were hanging on as Schalke continued to threaten with Farfan finding acres of space down the right against struggling left back Andre Santos.
The Londoners sent on Olivier Giroud for Gervinho to try to grab a late winner but instead it was Schalke who made the breakthrough with 76 minutes on the clock.
Afellay's header caught the defence flat-footed and Huntelaar this time made no mistake, slamming a shot into the net to send the fans behind the goal into wild celebrations.
Victory was secured in the 86th minute when Farfan again escaped Santos down the right and provided Dutchman Afellay with an unmissable opportunity.
It completed a miserable night for Arsenal who last tasted a home defeat in the Champions League against Manchester United in the 2008-09 semi-finals.
PORTO MAINTAIN PERFECT START
Two goals from Colombia striker Jackson Martinez handed Porto a hard-fought 3-2 win over Dynamo Kiev and allowed them to stay on top of Champions League Group A today.
The Ukrainians threatened to ruin Porto's day after coming from behind twice to level the match but could not prevent the Portuguese side from scoring the winner with 12 minutes remaining.
Silvestre Varela put Porto ahead after 15 minutes when he received the ball in the box from Argentine playmaker Lucho Gonzalez, gently cushioned it and then blasted it straight into the top right corner.
The Ukrainians replied swiftly and five minutes later Oleh Gusyev headed in an inswinging corner with Porto keeper Helton slow to react.
The home side went back on top 10 minutes before halftime through Martinez but in the second half were caught napping by the visitors and Nigerian Ideye Brown levelled again.
Martinez crowned his man-of-the match performance with a tap-in after 78 minutes, giving Porto a maximum nine points from three games.
The Portuguese club, in the Champions League group stage for the 17th time, put their experience to use as they kept calm to seal the win.
"Our first half was quality but although in the second we were not as strong, we achieved our goal," Porto coach Vitor Pereira said. "We grabbed nine points from the first three matches and in the Champions League, it's not any team that does that".
Kiev will take little heart from becoming the first team to score against Porto at the Dragao stadium this season in all competitions.
Paris St Germain are second in the group with six points after a 2-0 win at Dinamo Zagreb. Kiev are third on three points while Zagreb are on zero.
PSG DOMINANT IN 2-0 WIN
Paris St. Germain stayed on course to reach the Champions League last 16 after first-half goals from Zlatan Ibrahimovic and Jeremy Menez secured a 2-0 win at Croatian title holders Dinamo Zagreb.
PSG dominated from start to finish and should have won by a bigger margin, but for some wasteful finishing by Ibrahimovic who missed two great chances before he broke the deadlock in the 32nd minute with a crisp shot into the far corner.
Midfielder Menez broke down the left and weaved his way past two defenders before squaring the ball back into the heart of the penalty box for the Swedish striker to slide in and beat goalkeeper Ivan Kelava.
Menez made it 2-0 shortly before halftime, taking a Javier Pastore pass into his stride before he rifled a low drive between Kelava's legs on a grim evening for Dinamo.
Watched by only 7,000 home fans in their Maksimir stadium, Dinamo stayed on the back foot after the interval and had the woodwork as well as last-gasp defending to thank for not conceding more goals.
Their Brazilian-born midfielder Sammir, who made his debut for Croatia in Euro 2012 qualifying, showed flashes of brilliance but left to his own devices, he could not stop Dinamo from suffering their ninth successive defeat in Europe's premier club competition.