Two goals from Southampton striker Lee Barnard ended Norwich City's remarkable 11-match winning streak at Carrow Road.
Barnard scored in the 33rd and 77th minutes as Canaries fans saw the Coca-Cola League one leaders defeated on home soil for the first time since mid-September.
Norwich's woes were further underlined as they had Darel Russell dismissed in the 64th minute for violent conduct.
Second-placed Leeds failed to take full advantage as their recent stuttering form continued with a 1-1 draw with struggling Brighton at Elland Road.
Simon Grayson's side have now taken just seven points from the last 24 on offer, with their point today courtesy of another late goal, this time in the 95th minute from Robert Snodgrass.
Albion had taken a 77th-minute lead from Glenn Murray after he had been fouled in the area by Richard Naylor, only to be reduced to 10 men four minutes later when Adam Virgo was dismissed for serious foul play.
The top two's nearest challengers both kept up the pressure with home victories as third-placed Colchester beat Oldham 1-0 thanks to Danny Batth's first goal of his career.
The U's are within a point of Leeds, whilst fourth-placed Charlton are three points adrift following a 2-0 win over Yeovil courtesy of goals from Kyel Reid and David Mooney for their first win in six.
Meanwhile, Swindon remain in fifth place after a 2-0 win over Carlisle, while Huddersfield were also 2-0 winners at Hartlepool. The Terriers leapfrogged Millwall into the play-off places as the Lions suffered a shock 1-0 loss at relegation-threatened Wycombe.
Elsewhere, MK Dons eased to a 3-1 home victory over Southend, Tranmere and Walsall both enjoyed 2-1 home victories, Walsall beat Brentford at the Bescot Stadium, Gillingham saw off Bristol Rovers and rock-bottom Stockport finally ended their long wait for a win with a 1-0 victory over Exeter at St James Park.
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