Swansea City climbed above Arsenal in the Premier League thanks to a pair of goals in three second-half minutes at the Liberty Stadium.
For the second straight game, Arsenal threw away a lead following Alexis Sanchez's 12th goal in 14 games.
Swansea's goals came from an inch-perfect Gylfi Sigurdsson free kick and Bafetimbi Gomis header just two minutes after he had been introduced as a substitute.
Here, Sports Mole gives each player a rating out of 10 for their performance in sodden South Wales.
SWANSEA
Goal
Lukasz Fabianski: Would have needed an incredible save to deny Alexis, but was solid in keeping out the three other shots on target by his former employers. (6/10)
Defence
Angel Rangel: Probably didn't get forward as much as he usually likes to, but a decent display nonetheless. (6/10)
Kyle Bartley: Made just his second Premier League start in 21 months and came through the test well. Wasn't fazed by the likes of Alexis and Welbeck. (6/10)
Ashley Williams: Looked as if he might have to go off with an early injury, but soldiered on and was dominant in the air. (7/10)
Neil Taylor: Had a tough task keeping Alex Oxlade-Chamberlain quiet, but still managed to get forward and help in attack. (6/10)
Midfield
Ki Sung-Yueng: Made very few mistakes, but struggled to really have an impact on the game. (6/10)
Tom Carroll: Tentative in his play after being given the chance to shine with Jonjo Shelvey injured. Came off late on. (5/10)
Gylfi Sigurdsson: A stunning free kick which brought the Swans level. Apart from that, a quiet game by the Icelandic's standards. (7/10)
Attack
Marvin Emnes: Worked hard but did little before being taken off midway through the second half. Shot straight at Wojciech Szczesny with his one and only good chance. (5/10)
Wifried Bony: Proved a pest for the Arsenal defence with his strong, back-to-the-goal attributes. Should have won a penalty in the first half, but referee Phil Dowd disagreed. Came off for Gomis just after the equaliser. (7/10)
Jefferson Montero: The man of the match. Too quick for Arsenal and Calum Chambers in particular, going past the right-back on several occasions. He set up the winner with one of these bursts of pace and a well-directed cross. (9/10)
Substitutes
Bafetimbi Gomis: Scored the winner for his first Premier League goal with one of just five touches that he had in the final 15 minutes. Some impact. (7/10)
Modou Barrow: The Swedish teenager made his senior debut from the bench and looked impressive. Won the free kick for Sigurdsson's equaliser and also showed some neat touches. (7/10)
Leon Britton: A confidence-boosting brief appearance more than anything. It was his first game this season after a lengthy injury. (6/10)
ARSENAL
Goal
Wojciech Szczesny: Could do nothing about either goal. Pretty faultless for the rest. (6/10)
Defence
Calum Chambers: Perhaps the young England right-back's worst display since a summer switch from Southampton. He was ever so impressive last weekend against Burnley, but looked tired and unable to cope with Montero's pace this afternoon. A day to forget. (3/10)
Per Mertesacker: Made his 100th Premier League appearance for the Gunners and put in a decent showing. (6/10)
Nacho Monreal: Understandably looks out of his depth in central defence. Bullied by Bony. (5/10)
Kieran Gibbs: Got forward when he could. Must be glad he's not the one who's been shifted centrally and has to deal with the likes of Bony. (6/10)
Midfield
Alex Oxlade-Chamberlain: Made some early mistakes but grew into the game and was Arsenal's brightest spark. He did well to avoid a couple of challenges in the build-up to the opener. (7/10)
Mathieu Flamini: Barely noticeable in midfield for the Gunners. Came off with 10 to play. (5/10)
Aaron Ramsey: Almost scored a stunning volley at the end of the first half. Still looks like he's working his way back to full fitness. Withdrawn at the same time as Flamini. (6/10)
Santi Cazorla: Got a bit of a kicking from Swansea and never quite influenced the game like he can. Played the through-ball to Welbeck that resulted in Alexis scoring. (6/10)
Attack
Alexis Sanchez: Another goal for the Chilean - that's now 12 in his last 14 Gunners games. There's so much pressure on him to keep scoring and he faded in and out of the game today. (7/10)
Danny Welbeck: Provided the assist for Sanchez, but also squandered a clear-cut first-half opening. (6/10)
Substitutes
Theo Walcott: Given a little over 10 minutes to impress and messed up his one and only chance by failing to control a ball over the top. (5/10)
Jack Wilshere: Should have maybe started instead of Flamini. Had a late chance with the last kick of the game well blocked. (6/10)
Yaya Sanogo: Replaced Chambers in the last minute and didn't have time to impact the game. (6/10)