On an evening when Watford were as poor as the hosts were intense, goals in each half from Shane Long and Dusan Tadic took Southampton into 12th place and within two points of their underwhelming visitors.
Ronald Koeman began with a 3-5-2 formation - and with Ryan Bertrand one of his central defenders - and w ith England international goalkeeper Fraser Forster returning from a long-term knee injury
Throughout much of their disappointing recent run - they had lost eight of their previous 10 fixtures - Southampton had begun games encouragingly before their confidence deteriorated upon harshly conceding the opening goal or not converting their chances
It therefore came as little surprise that they were the more energetic of the two teams immediately after kick-off, even if the reality is their opening goal arrived when the threat appeared minimal.
Matt Targett, playing as a wing-back, received possession on the left wing before curling an accurate, 17th-minute cross into the penalty area towards Long - from where the forward neatly headed beyond goalkeeper Heurelho Gomes and inside the right post
Watford's response was to become even more sluggish, and erratic, and to allow Sadio Mane to run near-unchallenged from the left wing and to the edge of the penalty area before shooting and watching Gomes palm his effort wide
From the resultant corner, Targett - demonstrating his team's growing confidence - shot from distance before watching the ball being deflected off-target, and while Odion Ighalo provided an isolated response with a run and shot that was also deflected, the hosts otherwise remained in control.
The concern remained that with Watford's talent a one-goal lead would not be enough, and had they secured an equaliser, Mane - more than any other - would have felt responsible
After intercepting a rare misplaced pass from Jose Jurado, the forward found himself immediately in front of goal but instead struck the outside of the post
This was the worst performance the otherwise-impressive Quique Sanchez Flores has overseen since his appointment as Watford's manager, and he will know that had Mane not missed further chances, and Steven Davis' classy finish not been ruled offside, his team would have lost more heavily.
Pressure had been building on his counterpart, Koeman, but as if to highlight Southampton's poor run had reached its conclusion and that he remained firmly in control, the manager substituted Mane for Dusan Tadic and was almost instantly rewarded with a goal.
Controlling possession after Davis' header, Tadic ran into Watford's penalty area, created space, and classily finished low beyond Gomes from in front of goal in the 73rd minute.
In doing so, a crucial victory was secured, and unlike in the 4-0 defeat of Arsenal, this time winning appeared far from a one-off
Source : PA