Championship side Brentford produced a fine display to see off a near-full-strength Southampton side and book a Carabao Cup trip to West Brom.
Ralph Hasenhuttl named 10 of the side that started the Premier League season at the weekend but they were outplayed by last season's play-off finalists.
Midfielder Christian Norgaard opened the scoring with a thumping header.
And Josh Dasilva blasted home from the edge of the box after good work from Shandon Baptiste.
Saints fielded an attack of Nathan Redmond, Che Adams and Danny Ings but mustered just three shots on target all night.