Eric Hassli scored his second goal in a Saints shirt last night - within 60 seconds of the kick off.
But Ipswich went on to score four in reply to Hassli's opener and an own goal from centre-back Justin Miller, the Tractor Boys skipper.
That sent the visitors to the top of the FA Premier Reserve league, while Saints reserve team boss Steve Wigley and the watching Gordon Strachan left with a better idea of the quality coming up through the St Mary's ranks.
Hassli, on loan from Metz until the summer, did well to lob Mike Salmon before most of the 6,389 crowd had taken their seats.
Salmon blocked the Frenchman's initial effort but Hassli found the back of the net after reacting quicker than any of the Ipswich defenders.
The 20-year-old is still short of match fitness and on the hour, with Saints 3-2 down, he missed a good chance of his own making.
Hassli had smuggled his way past Miller and Thomas Gaardsoe, but sent the ball high and wide and into the Chapel End with his left foot when he had only Salmon to beat from ten yards.
Wide man Ulrich Le Pen equalised five minutes after Hassli's goal, capitalising on a poor Saints' clearance in rifling home left footed from 15 yards.
Then, on 18 minutes, Darren Ambrose grabbed the first of his two goals.
Ambrose was left with a free header after Le Pen had swung over a corner.
Just when Ipswich threatened to increase their lead, Saints were gifted an own goal through Miller but Scott McDonald should take some credit.
The Aussie, yet to be named in a first team squad under Gordon Strachan, broke clear down the left and his cross was turned in at the near post by Miller.
Ambrose capitalised on poor Saints marking in giving Ipswich a 3-2 lead on 54 minutes, sweeping another quality dead ball from Le Pen into Moss's far corner.
Bent grabbed a deserved goal after a moment that centre-back Luke Byles will want to forget.
Hamble product Byles was caught in possession by Bent, who stroked the ball past Moss from the edge of the area.
That completed the scoring four minutes from the end of a match that will have taught the Saints coaching staff a lot about the mettle of their rookies.
Wigley said: "We're providing the youngsters with the chance to show what they can do at this level. These end of season games are all about seeing as many of the young players who are coming through as possible."
Saints: Moss; Baird; Monk, Byles, Benali; Bleidelis; Crowell (Jones, 65); Davies; Howard; McDonald; Hassli. Subs not used: Williamson, Williams, Gleason, Lucas.
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