Will Smallbone's goal on the stroke of halftime was cancelled out within eight minutes of the restart by a quickfire Darwin Nunez and Mo Salah double.
Premier League top goalscorer Salah then added a second from the spot to ensure Liverpool took one step closer to the league title and nudged Saints closer to relegation.
Here's how we rated every Southampton player at Anfield.
**Aaron Ramsdale - 6.**
Beaten by an emphatic close-range effort by Nunez before conceding two spot kicks. Had produced an important save to deny Harvey Elliot before Liverpool's turnaround. Four saves.
**Kyle Walker-Peters - 6.**
Given more defensive duties as Ivan Juric switched to a back four. Beaten to a long ball by Luis Diaz in the first half but should have drawn a red card from Nunez. Pushed forward to the right wing after Dibling was withdrawn.
**Jan Bednarek - N/A.**
Had made a block to deny Salah before being forced off on 19 minutes with a concussion following a nasty collision with Ryan Manning.
**Taylor Harwood-Bellis - 6.**
Returned to the starting lineup for the first time since suffering an injury at Ipswich Town. Made three blocks and five clearances but should have done better with a first half header.
**Ryan Manning - 6.**
Handled Mo Salah for large portions of the game on his return to the starting lineup. Was only dribbled past once. Should keep his spot in the team.
**Lesley Ugochukwu - 5.**
Caught the eye with a fancy spin in the first half but was sloppy with possession after the restart. Was Southampton's most advanced player for goal kicks because of his hight.
**Will Smallbone - 6.**
Made the most out of a calamity at the back for Liverpool to give Saints an unlikely lead but was done by Nunez and VAR when conceding a penalty.
**Tyler Dibling - 5.**
Had moments where he was allowed to run at the Liverpool defence but was sloppy in possession before being replaced by Sugawara just after the hour mark.
**Kamaldeen Sulemana - 5.**
Also had space to run into on the transition but was not on the ball often enough, as evidenced by his 31 touches, the least of any player who played 90 minutes.
**Mateus Fernandes - 6.**
Played a role in causing chaos for Alisson and van Dijk, leading to Smallbone's opening goal. Pushed over for a blatant foul which was not given on the counterattack. Asked to lead the line at times.
**Albert Gronbaek - 6.**
Handed his first start since making his debut at Ipswich and did well in the hour he was given. Linked well with Fernandes on the break and found good pockets of space.
_**Substitutes**_
**Armel Bella-Kotchap - 6.**
His best performance since becoming an option for Southampton again this season. Some decent blocks and interceptions. Should start if Bednarek is not available against Wolves.
**Cameron Archer - 5.**
Came on after Liverpool had already turned the game around but delivered no impact from the bench other than a shot straight at Alisson.
**Yukinari Sugawara - 4.**
Punished for silly handball at a time when he needed to deliver a solid performance from the bench. Nothing is going his way at the moment.
**Joe Aribo - N/A.**
Came on with seven regular minutes to go and touched the ball just five times. Played in midfield this time rather than defence.
**Paul Onuachu - N/A.**
Came on alongside Aribo and also touched the ball just five times. Was shown a yellow card for pulling down Ibrahima Konaté outside the box.