Swansea piled on the misery for Arsenal as Michu scored twice in the closing minutes to clinch a shock 2-0 win at the Emirates Stadium on Saturday.
Spanish forward Michu, a £2 million signing from Rayo Vallecano this past July, underlined his growing reputation as the bargain buy of the season with a pair of clinical finishes on the counter attack, prompting Arsenal's fans to unleash a torrent of abuse at manager Arsene Wenger and his players at full-time.
Arsenal have now won just one of their last six Premier League matches and this defeat dropped the Gunners to 10th place in the table.
The north London club are now five points off the top four and to add insult to injury in-form Swansea climbed above them into seventh spot.
There was an early scare for Arsenal when they struggled to deal with Jonathan de Guzman's free-kick into the box and the ball fell to Swansea captain Ashley Williams in front of goal but a defender was in the way of the shot that followed.
Arsenal replied with a wayward effort from Carl Jenkinson but were soon back under pressure and needed goalkeeper Wojciech Szczesny to make a double save to deny Angel Rangel.
The full-back arrived at the back post to cap a superb passing movement that had seen almost every outfield player involved and Arsenal chasing shadows.
Arsenal moved Lukas Podolski from the left flank to the central striking position and the Germany forward saw a shot blocked by a defender before Santi Cazorla headed straight at goalkeeper Gerhard Tremmel from Jenkinson's cross.
Seconds later Swansea came even closer to taking the lead after Michu's header sent Nathan Dyer sprinting for goal, only for Thomas Vermaelen to slide in and block just as the winger unleashed his shot.
The half ended with Gervinho putting a free header so wide that Theo Walcott had to retrieve it from near the corner flag, and the home fans booed Arsenal off as soon as the whistle went.
The second half saw Jack Wilshere set Cazorla up for a low drive that Tremmel was able to block and referee Mark Clattenburg was not interested in awarding a penalty when Chico Flores body-checked Gervinho.
Swansea soaked up the pressure and replied with a shot from Itay Shechter that was deflected behind, before Rangel hit the side-netting after Cazorla had appeared guilty of a dive in the box at the other end.
Wenger made a double change in the 67th minute, with Olivier Giroud and Alex Oxlade-Chamberlain replacing Gervinho and Lukas Podolski.
Giroud went down straight away as Flores challenged but referee Clattenberg ruled the defender had got the ball.
Arsenal were applying strong pressure but Tremmel was behind Cazorla's volley.
Yet Swansea had not given up hope of snatching a winner and again Arsenal had Szczesny to thank for a smart save to deny Dwight Tiendalli after the substitute had moved into a shooting position on the right of the box.
Tremmel kept out Vermaelen's header at the other end and Swansea took full advantage of that escape as Michu netted with just two minutes remaining.
The Spaniard played a one-two with substitute Luke Moore which was deflected back into his path and he slotted calmly past Szczesny.
Swansea sealed the win in stoppage-time when Dyer caught Jenkinson in possession to send Michu away and again he made no mistake with only Szczesny to beat.
The final whistle was greeted by loud jeers from the home support as the away supporters celebrated a famous and fully deserved victory.