Relegation from the Premiership to the 'Fizzy Pop' League was bad enough.

But last night a teenager called Giles Coke heaped more misery on sorry Saints.

Three months after being sent down to the Coca Cola Championship, Mansfield midfielder Coke's first senior goal dumped Saints out of the Carling Cup.

It was a thoroughly deserved victory for a Mansfield side that dominated the second half at their nondescript Field Mill ground.

Third from bottom of League Two they may be, but they showed a young Saints side that there is a significant difference between the Carling Cup and the FA Youth Cup.

It was men against boys but the irony was that Mansfield midfielder Coke is still only 18 and was the toast of the Nottinghamshire town when he slipped the ball under the body of Saints goalkeeper Paul Smith in the 69th minute.

With Saturday's game against Plymouth in mind, Saints manager Harry Redknapp made 11 changes from the side that drew 2-2 at nearby Derby County.

He rewarded the youngsters that overcame Southend 3-0 at Roots Hall in the previous round with the chance to show that they are worth a regular place in his Championship side.

But they failed to do so against a well organised Mansfield that made a mockery of their league position.

Only two sides - Bury and Torquay - are below Mansfield at the foot of the Football League pyramid and their manager Carlton Palmer had resigned at the weekend after a loss at Rochdale.

But they responded under their caretaker manager Peter Shirtliff by inflicting a first defeat on Saints for six weeks - it was also Mansfield's first win since mid-August.

It may have been different if Saints had scored in the first half, when they created their only clear cut chances.

In the very first minute Dexter Blackstock hooked over the bar after Kenwyne Jones had had a shot saved by Kevin Pressman.

And on 31 minutes a Blackstock header from Yoann Folly's right flank cross was beaten away by the veteran keeper.

Martin Cranie won a corner with a 20-yard strike that Pressman failed to hold on the stroke of half time, but by then Mansfield had threatened on more than one occasion.

Adam Birchall, a former Arsenal trainee, just failed to turn home a cross from strike partner Richard Barker that flashed across Smith's six yard box and Simon Brown had a 36th-minute strike well saved by the Saints keeper.

Smith produced his best save of the night in the 41st minute, when he tipped over a Birchall effort. And in first half injury-time Barker and Blackstock just failed to convert crosses.

But it was all Mansfield after the break.

Smith dived low to his left to keep out a 50th-minute drive from the excellent Brown, and on the hour Mansfield's right-sided midfielder sent a dipping drive over the bar.

The home side were also a threat on the left flank.

Gareth Jelleyman headed straight at Smith and sent a dipping volley narrowly wide from 35 yards midway through the second half.

Coke scored the winning goal moments later.

After latching on to an exquisite through ball from Brown, he capitalised on a mix-up between Matthew Mills and Smith before slotting the ball past the static Saints keeper.

Instead of provoking a fightback, it knocked the heart out of Saints. A deflected free-kick from Birchall, and a drive from Fraser McLachlan, both went over the bar as the Field Mill faithful began to chant 'Easy, Easy'.

Redknapp introduced Theo Walcott for his League Cup debut in the 72nd minute. The 16-year-old raised Saints hopes briefly in the closing stages when he left full back Gavin Peer on his backside in the penalty area.

But he was not on the pitch long enough to stamp any authority on the game.

And he and the rest of Southampton's side were a chastened bunch as they made their way to the car park at Field Mill while Coke enjoyed his moment in the limelight in front of the Sky Sports cameras.