Goals from Michael Obafemi and Nathan Redmond earned Southampton a surprise 2-0 win at Chelsea in the Premier League on Thursday.
Obafemi broke the deadlock with his first goal of the season, bursting inside from the right and curling into the top corner after a tight opening half hour.
Frank Lampard changed his side's formation from 3-4-3 to 4-2-3-1 at the break and nearly earned an instant dividend as substitute Mason Mount set up Tammy Abraham, who flashed a shot into the side netting.
Saints winger Redmond was denied by Kepa Arrizabalaga on the break but coolly finished for the visitors' second after an impressive team move to silence Stamford Bridge.
The hosts struggled to break down Southampton's tight defence, and Ralph Hasenhuttl's side rise to 14th, three points clear of the relegation zone, building on last weekend's win over Aston Villa.
Chelsea stay fourth with 32 points from 19 games and must pick themselves up for their visit to Arsenal on Sunday.