Philippe Coutinho pulled one back for Liverpool right on the stroke of half time, but Jay Rodriguez restored the two-goal lead with a fine solo effort in the second half as Southampton picked up all three points.
Here, Sports Mole takes an in-depth look at what could prove to be a pivotal day in Southampton's quest for Premier League survival.
On target 12
On target 6
Was the result fair?
Yes. Southampton were the better side from start to finish and perhaps should have scored more than the three they managed. Liverpool struggled to create chances, while the Saints had a number of really good ones that they squandered. Their second goal had an element of luck about it but it was nothing less than what they deserved and Liverpool never really looked like getting back into it after that one.
Very impressive. If they perform like that week in, week out, then they will have no troubles avoiding the drop this season. They played some lovely football and Liverpool couldn't cope at times. They mixed long, aerial balls up to Lambert with fluid passing moves so the Liverpool defence had no idea what to expect each time Southampton came forward.
Poor. It has been the story of Liverpool's season - two steps forward and one step back. They came into the match in fine form but showed no signs of that as they were outplayed from start to finish in pretty much every area of the pitch. Luis Suarez did not have one of his best games for Liverpool and that had a big impact on the rest of the side, most of whom were also under par.
Sports Mole's man of the match
Adam Lallana: It's hard to pick out just one player from the Southampton side to name as man of the match as they all played well as a team. Captain Lallana, though, led by example throughout and nullified the threat of Steven Gerrard and Philippe Coutinho while proving dangerous on the attack himself.
It was a relatively gaffe-free game so there isn't much to choose from for this 'award'. It will have to go to Daniel Sturridge for turning his back on the ball in the wall, however. The striker showed exactly what not to do in a defensive wall when he turned away from the strike, creating a gap which the ball found via a deflection off him. To make things worse for Sturridge, the ball ended up in the back of the net, making it 2-0 to Southampton.
Phil Dowd won't have too many easier games to referee than this one. There were no major controversies and the only card he handed out was in the 91st minute. That one was a bit harsh but, on the whole, Dowd had a very solid match.
Southampton: Southampton will look to build on this big win when they host Chelsea at St Mary's at the end of the month.
Liverpool: Liverpool face another relegation candidate on March 31 when they take on Aston Villa.