An inspired Southampton earned a crucial win in their battle against relegation as they all but ended Liverpool's top-four hopes.
The hosts stormed ahead when Jay Rodriguez nodded down for Morgan Schneiderlin to steer in a shot.
Rickie Lambert's deflected free-kick added Saints' second before Philippe Coutinho slotted in for the visitors.
But Rodriguez completed a home win when he side-footed in after his initial shot was saved by Brad Jones.
At a rain-lashed St Mary's, the final whistle was the signal for Southampton to revel in only a second win in eight games as they moved seven points above the relegation zone.
The south-coast club have now beaten Liverpool in four of the last five league games at home and the out-of-sorts visitors could have little complaint at the result.
Liverpool captain Steven Gerrard said he wanted the Reds to have a
But his team were off the pace from the start and any lingering aspirations of Champions League qualification appear to have been ended by a first defeat in four games.
Liverpool boss Brendan Rodgers refused to get carried away after the 3-2 win over Tottenham last Sunday and was proved right as the inconsistency which has blighted his side's season struck again.
The hosts took the lead after six minutes: Gaston Ramirez flighting a left-footed cross to the far post where Rodriguez cushioned a header down for Schneiderlin, who guided past goalkeeper Jones from six yards.
The home side were scything through Liverpool seemingly at will and Southampton skipper Adam Lallana sent a half-volley fizzing over after the Reds failed to clear their lines.
Lambert also beat the offside trap to race clear, only to have his shot saved by the onrushing Jones.
Liverpool centre-back Martin Skrtel looked rusty as he made his first start in a month - and his foul on Lambert led to Southampton's second, with the Saints striker's free-kick deflecting in off Daniel Sturridge.
The movement and menace of Rodriguez was a key feature of the home side's attacking verve and, after Lallana's shot had been parried across goal by Jones, the forward's half-volley on the swivel went just high of a gaping goal.
Liverpool belatedly and briefly raised themselves towards the end of the first half as Glen Johnson sent Coutinho clear, with the Brazilian's shot being blocked after keeper Artur Boruc came out to save.
Coutinho had a spell on loan at Espanyol under Saints manager Mauricio Pochettino last season, with his former boss describing him as this week.
And he atoned for his miss when he pulled one back on the stroke of half-time.
A Luis Suarez cross was nodded back across the home goal by Gerrard and, after Sturridge's shot was blocked, Coutinho pounced to slot in.
Both defences had an air of vulnerability about them after the break, although neither team could capitalise.
Sturridge scuffed a shot wide after a Gerrard cross was only partially cleared, while Lallana was played through before his steered shot from a tight angle was saved.
Liverpool struggled for any cutting edge and Rodriguez compounded their misery with his late goal.
The forward waltzed through the Liverpool defence and, after his first shot was saved by Jones, Rodriguez slotted in the rebound to secure a deserved three points.
Liverpool manager Brendan Rodgers: "It certainly wasn't how we have been playing in the past few weeks.
"We didn't get going until it was 2-0 down. We conceded poor goals which has been unlike us and we are disappointed at that.
"We never really got started. It certainly wasn't the level we have been at and it was one of those days for us."