A comfortable win over League One Bristol City saw Southampton progress to the last sixteen of the Capital One Cup.
Mauricio Pochettino opted to make wholesale changes from the side that beat Liverpool on Saturday, changing the entire starting eleven, introducing academy products Calum Chambers and James Ward-Prowse.
Bristol City manager Sean O'Driscoll opted to change goalkeepers, as Frank Fielding made way for Elliot Parish.
Southampton had the first chance of the game, as Jack Cork managed to lift a floated pass towards the area, but Gaston Ramirez found his opportunity snuffed out by an interception on the blind-side.
Cork was involved in a creation of another chance, when his slack pass gifted Bobby Reid the ball thirty yards from goal. Jos Hooiveld was forced into accepting a yellow card for a cynical body-check as Reid attempted to fuel the counter-attack against Hooiveld and Maya Yoshida.
Following an elaborate set-piece ruse, Jay Emmanuel-Thomas stepped up for the strike, which deflected behind for a corner following a block from Tadanari Lee. The corner was easily dealt with, by the home side's stand-in goalkeeper Kelvin Davis.
The Saints had to wait twenty-six minutes to break the deadlock in the previous round against Championship side Barnsley, but the wait was to be shorter on this occasion.
Southampton stringed together a sequence of sharp passes before Ward-Prowse took aim, the youngster's shot rebounded to Ramirez, who thumped a volley into the top corner to hand the Premier League side the advantage.
Ramirez had added the fifth goal in Southampton's 5-1 demolition of Barnsley in the previous round, with a mazy run that preceded an impressive chipped finish.
Bristol City attempted to make a quick comeback, but Davis was swiftly off his line to dive at the feet of the onrushing Reid, who had been picked out by Stephen McLaughlin.
Lee succeeded in springing the visitors' offside trap towards the half-hour mark, when his smart run off the shoulder was spotted by Ward-Prowse, but his attempt on goal was turned over the bar by Parish.
Ramirez caught side of the opportunity to double his tally for the night, but his swirling attempt from 25 yards flew just wide of the post, causing Parish to breathe a sigh of relief.
The Japanese forward found himself another chance in the penalty area, after a dummy run and smart swivel worked open an opportunity that forced Parish to turn the ball behind for a corner.
Emmanuel-Thomas latched onto a direct pass at the other end of the pitch, as some smart foot-work presented him with clear sight on goal, but Davis was equal to the effort and denied the former Arsenal man with a smart save.
The resulting corner was swung in deep, but once again Davis read the flight of the ball perfectly and gathered with relative ease.
Guly Do Prado capitalised on some good build-up play to deliver a low ball across the face of goal, but first Lee and then Ramirez failed to convert the opportunity.
Danny Fox and Steven Davis were next to combine, presenting Do Prado with an opportunity to extend Southampton's lead on forty minutes, but the Brazilian fluffed his lines and failed to get his attempt on goal.
Do Prado was involved for a third time soon after, after combining well with Ramirez, who then lofted a shot on his weak foot, before watching it drift wide of the post.
Bristol City had another chance to level the scores, as Brendan Moloney swung in a free-kick from deep, on to the head of the onrushing Derrick Williams, who could only head over Davis in the Saints goal.
Calum Chambers' darting run down the flank almost provided the second goal via a freak turn of events. The full-back's cross clipped Joe Bryan, which almost caused the ball to elude Parish in the Robins' goal. Fortunately for O'Driscoll's men, the 'keeper was able to bring out some sharp foot-work to enable him to turn the ball over the bar.
Cork almost laid claim to his first goal in Southampton colours, when Ward-Prowse's corner was cleared as far as the former Chelsea man. His powerful strike stung the hands of Parish in the City goal, but the ball was parried to safety.
Yoshida went close in first half stoppage time, connecting with a Ward-Prowse corner. Unfortunately for the Japan international, he headed over following an inviting header across goal from Cork.
The sides went in at the interval with just one goal between them and following the break neither had opted to make a change during the break.
Southampton were to have the first attempt on goal of the second half, when Do Prado evaded his marker to get on the end of a Ward-Prowse whipped corner, but Parish was on hand to deal with the headed attempt.
Bristol City hit back at the hosts with renewed vigour, as Bryan was first to test Davis just six minutes into the second half at St. Mary's. Davis had to get down low to turn the midfielder's attempt wide of his post.
Bryan was involved against just minutes later, when a foraging run down the left-flank produced a cross for Emmanuel-Thomas, who could only poke wide of the target.
City kept their foot on the pedal, with Reid next to force Davis into action. Reid's swerving effort nearly caught Davis off-guard, but the former Sunderland stopper managed to push the swerving effort just over the crossbar.
The scores should've been levelled when Emmanuel-Thomas carried out some good work left of the area before poking the ball towards the path of McLaughlin, who failed to connect with the inviting ball at the back post.
Marlon Pack was next to try his luck, but his shot flew too high and failed to trouble the Southampton defence.
With twenty minutes remaining, Marlon Harewood was introduced by O'Driscoll as he sensed the opportunity to get back into the game. Bryan was withdrawn to make way for Harewood.
Just three minutes later, Southampton boss Pochettino readied two substitutes of his own as he hoped to swing the pendulum back in the favour of the hosts. Jay Rodriguez and Harrison Reed handed an opportunity as Lee and Do Prado made way.
It was to be Reed's first senior appearance at St. Mary's, although not his first in a Southampton shirt. Reed, 18, was introduced as a second-half substitute in Southampton's 5-1 win over Barnsley in Round Two.
O'Driscoll shook his options up again, replacing Scott Wagstaff with stalwart Neil Kilkenny, formerly of Leeds United.
Pochettino's substitutes almost combined to immediate effect.
Reed's centre picked out Rodriguez, but the onrushing forward could only scoop his effort into the stand behind the goal.
Reed continued to impress during his short cameo, providing short sharp runs into space to open up opportunities for his team-mates. Reed carved a chance for himself before whipping a ball across the face of goal, which eventually deflected behind for a Southampton corner.
Once again, Ward-Prowse stepped up to launch an in-swinging corner into the penalty area, and perfectly into the path of Hooiveld, who headed home with aplomb.
It was Hooiveld's first goal for Southampton in seventeen months, having last scored in February 2012 in a 1-1 draw against West Ham United at Upton Park.
With just five minutes remaining and defeat seemingly inevitable, O'Driscoll brought on former MK Dons striker Sam Baldock in place of the lively Reid.
Just moments later, Pochettino also opted to use his final change. Development squad winger Omar Rowe was given another taste of first-team action, as he replaced goalscorer Ramirez for the closing minutes of the tie.
Ward-Prowse teed himself up for a late attempt, but his powerful effort evaded everyone and flew wide of the target as the seconds ticked down.
The draw for the Fourth Round of the Capital One Cup will be made after Manchester United vs Liverpool on Wednesday night.
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