Liverpool’s hopes of a top-four spot were dented as Southampton dramatically snatched victory at St Mary’s.
Liverpool had looked in command after Philippe Coutinho and Daniel Sturridge scored in a five-minute period.
Sadio Mane missed a penalty just after the break following Martin Skrtel’s foul on Graziano Pelle, but made amends soon after with a smart finish.
Pelle’s curling shot restored parity in the 83rd minute, before Mane pounced to seize all three points for his side.
Liverpool pressed forward to try and force a final twist, but a speculative penalty shout for a push on Christian Benteke was all they could muster.
Southampton remain seventh, with Liverpool two places lower and still seven points off the top four before Sunday’s Manchester derby.
Reds’ first half…
As the Reds departed the south coast, manager Jurgen Klopp was left to try and comprehend how they had contrived to lose from 2-0 up at half-time for the first time in the Premier League.
After Shane Long was denied an early penalty in a tussle with Dejan Lovren, the Reds took control of the first half with Coutinho’s low curling effort followed in short order by Sturridge’s cleverly-crafted second.
As Southampton searched for an immediate response, Liverpool exploited the space left behind with Joe Allen shooting into the shins of Fraser Forster from eight yards before seeing a goal chalked off for offside.
However, whether it was Thursday evening’s Europa League exploits or the 10 games more they have played than Saints this season, Liverpool’s slick passing and swift movement dried up markedly after the break.
When Mane’s penalty – awarded after Skrtel’s tug on Pelle – was pushed aside by goalkeeper Simon Mignolet early in the second half, it seemed that it was set to be the visitors’ day.
But Ronald Koeman’s introduction of Mane and Victor Wanyama at half-time throttled the supply to Liverpool’s front men while adding a more clinical edge to his own attack.
After the electric Mane had escaped Mamadou Sakho to cut the deficit, the hosts kept believing as Liverpool kept retreating and the pressure finally told late on.
Sturridge – who played 68 minutes as his side completed a 3-1 aggregate Europa League win over Manchester United in midweek – had already been withdrawn wincing by that point, with full match fitness still some way away.