Defeat for youngsters at Eppleton.
Sunderland U21 0 Southampton U21 1
Sunderland's under-21s suffered their first league defeat since the opening day of the season on a bitterly cold evening at Eppleton CW.
Callum Chambers' goal 20 minutes in was enough for the Saints, who completed a league double over the Black Cats having won 4-3 on the south coast back in August.
Kevin Ball handed a run-out to striker Connor Wickham, who had a couple of chances but couldn't find a way past Saints keeper Chris Johns.
Meanwhile, Jordan Pickford pulled off a number of saves at the other end to frustrate the Saints, who leapfrogged Sunderland in the Barclays U21 Premier League with the win.
The visitors had an excellent chance within the first minute through striker Sam Hoskins, who bought a yard of space only to place a low left-footed shot across goal.
With both sides toiling manfully in freezing conditions, the visitors gave themselves a winter warmer with what proved to be the only goal 20 minutes in.
Lloyd Isgrove's corner from the left was measured perfectly for Chambers to steal in and head the ball beyond Pickford, who had no chance.
Saints were grateful to keeper Johns for denying the hosts just before the half hour as he produced an excellent save to deny Adam Reed at close range after the midfielder latched on to an excellent through ball.
Jordan Laidler then headed over just before the break and Wickham thought he'd scored just after the restart, seeing his header deflected over from close range after Craig Lynch nodded Laidler's cross-shot back across the box.
Wickham then fired straight at Johns as Sunderland pushed for an equaliser, but it wasn't to be and Pickford was the busier of the two goalkeepers in the closing stages.
He did brilliantly to push away Jack Cork's speculative effort and then dived bravely at the feet of Isgrove as he bore down on goal.
Sub Joe Curtis tested the Sunderland keeper with a low drive late on as the Saints finished on the front foot to make sure of victory.
Sunderland: Pickford, Marrs, Adams, Oliver, Ferguson, Reed (c), Gorrin (Armstrong, 74), Mitchell, Lynch, Wickham, Laidler (Deacon, 74).
Subs Not Used: Dixon, Harrison, Joyce.