Southampton came from behind to earn their second win of the fledgling Premier League season and move above a Chelsea side lacking cohesion and a cutting edge at St Mary’s.

But another former Manchester City player levelled moments later, with Romeo Lavia firing a superb effort beyond Edouard Mendy after Chelsea failed to properly clear a corner.

From then on Southampton were the better side and scored what proved to be the winner before the break, when Romain Perraud picked out Adam Armstrong and his effort deflected off Kalidou Koulibaly and into the net.

Ralph Hasenhuttl’s outfit climb to seventh as a result of the deserved victory, level on seven points with Chelsea but above them on goals scored.

Saints’ summer signings prove a hit

Southampton are so often a breeding ground for young players looking for a break in the top flight and appear to have recruited another gem in Lavia, who spent two years at City after leaving Anderlecht, before joining the Saints this summer.

The midfielder and 20-year-old German defender Armel Bella-Kotchap, another shrewd acquisition, provided the foundations for an impressive Southampton performance that earned them a first win over Chelsea in three years and first at St Mary’s since March 2013.

Chelsea had been the better side early on and capitalised through Sterling, but a slight mix up saw Cesar Azpilicueta put the ball behind for a corner and it was only cleared as far as Lavia – the 18-year-old Belgian took a touch before rifling a strike past Mendy from the edge of the area.

The hosts were outdone in terms of possession in the first half but looked far more efficient with the ball after Lavia’s leveller and a swift move led to Armstrong putting them ahead in added time from Perraud’s cutback.

That Lavia – the first player born in 2004 to score a Premier League goal – had to be replaced just before the hour mark after pulling up will be a concern for Hasenhuttl, with the youngster already proving to be an integral part of his side.

Bella-Kotchap, who made a great recovery tackle on Sterling early in the game, and Mohammed Salisu were formidable at the heart of Southampton’s defence and gave Chelsea little encouragement of finding a way back.

At the other end, Marc Cucurella stopped Southampton adding to their lead with an instinctive block from Mohamed Elyounoussi’s header and Thiago Silva then cleared a Salisu effort off the line as the hosts continued their encouraging start to the campaign.