Arsenal’s hopes of landing a first league title in 12 years suffered a heavy blow as Swansea came from behind to win at Emirates Stadium.
Joel Campbell slid to hook the Gunners into an early lead and they looked set to make up ground on leaders Leicester.
Swansea – missing boss Francesco Guidolin through illness – levelled when Wayne Routledge side-footed home.
Olivier Giroud and Alexis Sanchez struck the bar before Ashley Williams pounced to earn a crucial Swansea win.
The Welsh club now have a six-point cushion to the relegation zone but Arsenal’s six-point deficit to Leicester City at the top of the table looks sure to yield ugly headlines.
Arsene Wenger’s side have lost three successive games for the first time since 2010, severely damaging their title hopes in a season which many regard as their best opportunity in recent times to be crowned champions.
After defeat at Old Trafford on Sunday, pundits lined up to criticise Arsenal’s failings. Their shortcomings were again laid bare against the Swans as they missed chances and their soft centre again cost them dear.