A late try by reserve hooker Johnny Mason gave Southern a narrow win over Alhambra-Union at the North Ground.
Both teams were tentative and concentrated on defence in a game that never rose to great heights.
Southern had camped inside the Alhambra-Union 22m for the last eight minutes but its repeated attacks had been repulsed.
The winning try came with just two minutes left, after Southern had won three lineouts and Mason charged for the line and scored out wide.
Only two tries were scored in the game and Alhambra-Union looked to have sealed the win when big No 8 Regan Turoa crashed over in the corner with eight minutes to go, giving the home side a 13-9 lead.
The return of tighthead prop Scott Manson after injury had boosted the Alhambra-Union pack and it controlled possession and territory in the first spell.
Locks Matt Kissick and Jeremy McKee were having strong games and they were backed by blindside flanker James Willocks.
But good defence by Southern, and poor option taking and ill-directed passing, meant the advantage was not turned into points and the first half ended in stalemate at 6-6.
Flanker TJ Ioane was a dynamo in the Southern pack, breaking the gainline every time he touched the ball, and No 8 Tom Franklin and lock Sam Gibson won lineout ball.
Ben Patston gave direction to the Southern backs when he came on in the second spell and powerful centre Apelu Alapati was a handful for the defence.
Southern 16 (Johnny Mason try; Bryce Hosie 2 pen, Ben Patston con, pen), Alhambra-Union 13 (Regan Turoa try; Peter Breen con, 2 pen). Halftime: 6-6.
