James Ward-Prowse, Jay Rodriguez and Dusan Tadic condemned Leicester to their 11th Premier League defeat of the season as Southampton triumphed 3-0 at St Mary's.
The reigning champions have now lost half of their Premier League matches this term, to sit just five points above the relegation zone.
Southampton eased to victory, leaving Claudio Ranieri's Leicester looking short of ideas in attack and worryingly frail at the back.
TWEET OF THE MATCH
"Watching Leicester return to their mediocre selves this season may be irritating, but bizarrely it's so much less stressful." - Gary Lineker (@GaryLineker).
Dusan Tadic. While others might have done the damage on the scoresheet before his late penalty, Tadic was the constant probing threat between the lines that Leicester struggled to contain.
MOMENT OF THE MATCH
James Ward-Prowse's neat finish capped a fine flowing move where Nathan Redmond and Cedric Soares combined neatly to tee up the midfielder to slot home.
CALAMITOUS DEFENDING UNDOES LEICESTER
The Foxes are all over the place at the back this term, so at odds with their miserly defending when winning last term's Premier League title. Robert Huth and Wes Morgan are shadows of their former selves and mistakes from both proved costly here.
Fraser Forster 7 (out of 10)
Cedric Soares 8
Virgil Van Dijk 8
Maya Yoshida 6
Ryan Bertrand 8
Pierre-Emile Hojbjerg 6
Oriol Romeu 7
James Ward-Prowse 7
Dusan Tadic 9
Nathan Redmond 7
Jay Rodriguez 8
Jordy Clasie (for Hojbjerg, 72) 6
Shane Long (for Rodriguez, 79) 6
Jack Stephens (for Van Dijk, 55) 7
Kasper Schmeichel 6
Danny Simpson 5
Wes Morgan 4
Robert Huth 3
Christian Fuchs 4
Wilfred Ndidi 5
Danny Drinkwater 5
Nampalys Mendy 6
Demarai Gray 6
Shinji Okazaki 6
Jamie Vardy 5
Ahmed Musa (for Okazaki, 62) 5
Marc Albrighton (for Mendy, 46) 5
WHO'S UP NEXT?
Liverpool v Southampton, EFL Cup semi-final, January 25
Derby v Leicester, FA Cup fourth round, January 27