Steven Fletcher's strike proved the difference today as Sunderland took all three points from their long trip to fellow strugglers Saints.
The Scotland international's effort just before half-time ultimately separated the sides in a tense encounter at St Mary's.
Only a point separated 16th-place Sunderland and the hosts coming into the match, with Saints just one place worse off than the north-east side.
Martin O'Neill's side had lost three of four matches in December but looked dangerous from the outset, with Stephane Sessegnon forcing an exquisite save from former Black Cats goalkeeper Kelvin Davis in the opening minute.
A deflected Rickie Lambert free-kick was the closest Saints came in a first half in which Fletcher swept the opener home late on.
Saints pressed for a leveller throughout the second period but looked devoid of ideas and were unable to find a way past Sunderland, who held on for their second away win of the season.
Fletcher, Adam Johnson and Danny Rose all overcame knocks to start for the hosts, who came close in the opening seconds as Davis superbly denied Sessegnon from 25 yards.
John O'Shea nodded over from the resulting corner much to the relief of Southampton, who were jolted into action by the Black Cats' explosive start.
Sebastian Larsson was denied by Davis when Sunderland returned to the attack, before Fletcher directed a Gardner cross just wide and James McClean saw a tame effort from distance saved.
O'Neill's side were looking the bigger threat but record signing Gaston Ramirez was proving a thorn in their side.
Simon Mignolet did well to deal with an awkward dipping effort from 20 yards before the Uruguay international curled over from distance.
Both sides were playing cautiously in a bid to find the opener, with the defences dealing with any potential threats.
First Cuellar denied Lambert as he prepared to break through on goal and then Maya Yoshida did well to stop Fletcher meeting a driven Gardner cross from the right.
Puncheon saw a strike blocked by O'Shea as Saints looked to end the half on top, only for Fletcher to break the deadlock.
Johnson's low cross from the left was played on by Sessegnon for the Scotland international to sweep home a 42nd-minute opener.
Referee Howard Webb waved away Mayuka's penalty appeals as the first half came to a close, with Lambert firing just over 30 seconds after the restart.
Sunderland could have had a second had somebody connected with a drilled Gardner effort before Johnson fired over, leading Adkins to shuffle the pack.
Steve de Ridder, making his first Premier League appearance of the season, and Steven Davis came on for Mayuka and Schneiderlin.
De Ridder almost made an immediate impression as he found Jose Fonte with a corner, but the Portuguese defender could only nod wide.
Sunderland, though, were frustrating a Saints side lacking inspiration as the rain hammered down.
Puncheon was dispossessed as he ran through on goal and Steven Davis saw a shot blocked by Jack Colback as the hosts desperately sought a leveller.
Davis saved an audacious Gardner free-kick from range, before Guly do Prado came on for Puncheon in a final throw of the dice by the hosts.
However, Southampton had a late penalty appeal waved away and Do Prado saw a stoppage-time shot blocked, meaning the 1,814 travelling fans would leave happy.