Southampton completed a stunning first-half turnaround to inflict Chelsea's second defeat of the season with a deserved 2-1 victory.

Thomas Tuchel's side are now five points behind leaders Arsenal having taken only seven points from their first five matches despite their evening on the south coast starting perfectly when Raheem Sterling netted his third goal of the season from close range.

But Southampton fought back through talented teenager Romeo Lavia, who blasted home from the edge of the area to lift a subdued St Mary's.

Saints never looked back from there with Adam Armstrong firing home the winner in first-half added time to leave Ralph Hasenhuttl's side above the Blues.

How super Saints marched on

Chelsea have delivered a mixed bag of performances so far this season and it was evident in the first-half alone. For 20 minutes they were sharp, resilient and deservedly went ahead through Sterling as he swivelled to put home Mason Mount's pull-back.

Southampton needed a spark and impressive 18-year-old midfielder Lavia delivered it. James Ward-Prowes' corner was poorly cleared by Cesar Azpilicueta to the edge of the box where the Belgian took a touch before hammering a piledriver into the corner which flashed past Edouard Mendy.

Saints were on top from then on, capitalising on their pressure in added time when Romain Perraud smartly picked out Armstrong in the box, who controlled sharply before firing into the corner via a slight deflection off the left leg of Kalidou Koulibaly.

Chelsea were angered by Che Adams fouling Jorginho on the half-time whistle and flicking the ball into his face yet couldn't turn it into momentum after the break.

Instead, Southampton were twice denied by brilliant goalline clearances. The first saw Mohamed Elyounoussi's header hit the shoulder of Marc Cucurella before Thiago Silva flicked Mohammed Salisu's effort away.

Southampton got better and better while Chelsea toiled, unable to gather any momentum, clearly missing the raiding Reece James, and slipping to another worrying defeat.

What's next?

Southampton travel to Wolves as their fixtures become more favourable with Brentford, Aston Villa and Everton to follow.

Chelsea host West Ham in a Premier League London derby on Saturday at 3pm.

Teams

Southampton Bazuna, Walker-Peters, Bella-Kotchap, Salisu, Perraud (Djenepo 73), Lavia (Aribo 60), Ward-Prowse (c), Diallo, Elyounoussi, A. Armstrong (Lynaco 86), Adams
Subs Not Used McCarthy, S. Armstrong, Mara, Walcott, Bednarek, Valery
Booked Salisu, Ward-Prowse
Goals Lavia 28, A. Armstrong 45+1

Chelsea Mendy, Azpilicueta (c) (Chilwell 67), Silva, Koulibaly, Cucurella, Loftus-Cheek (Kovacic 46), Jorginho (Broja 67), Mount, Ziyech, Havertz (Pulisic 66), Sterling
Subs Not Used Kepa, Ampadu, Chukwuemeka, Gilmour, Vale
Booked Pulisic
Goals Sterling 23

Attendance 31,452

Referee Michael Oliver

VAR Michael Salisbury