Match ends, Southampton 0, Brentford 2.
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.
Substitute Shane Long went close for the Saints but the Bees easily saw out the win.
- Follow reaction from tonight's action here.
Brentford could only name five substitutes after a positive Covid-19 test in the squad led to some players having to quarantine, and left big-money striker Ivan Toney out, yet still had enough to progress.
Bryan Mbeumo saw a shot cleared off the line after an error from Saints keeper Alex McCarthy before Adams wasted the hosts' best chance of the night when he hit the post from a good position.
Norgaard was left free to head in Mbeumo's delivery and put Thomas Frank's side ahead, and their lead was doubled before half-time when England Under-21 midfielder Dasilva placed home accurately.
'We showed we can compete'
Brentford boss Thomas Frank:
"It was a performance where we definitely showed we can compete with a Premier League opponent.
"But we all know that we need to do that more than one game to go forward. And it's very important for me to mention that.
"We are very pleased. Wins give more confidence - that's why I am pleased we progressed - and this win, this performance and this feeling we need to take into the game on Saturday."
Southampton manager Ralph Hasenhuttl:
"We have to be very, very clear that at the moment, with the team we have, it will be very difficult to win games.
"We were not quick enough at any part, not physically and not mentally.
"This is definitely something that we should work on. We played too slow and we did not do enough with the ball.
"Some of our players are not as strong as we have seen them in the past. We have a few big problems but we know that it is a tough season and a long season and we have to get back to working well.
"There is definitely a lot of work to do."
- 1McCarthyBooked at 8mins
- 23TellaSubstituted forObafemiat 84'minutes
- 11RedmondSubstituted forDjenepoat 71'minutes
- 10AdamsSubstituted forLongat 84'minutes
- 22DalsgaardBooked at 52mins
- 4GoodeBooked at 58mins
- 29Bech Sørensen
- 2ThompsonBooked at 12minsSubstituted forHenryat 71'minutes
- 14DasilvaSubstituted forMarcondesat 71'minutes
- 15ForssSubstituted forDervisogluat 77'minutes
- John Brooks
- Shots on Target
Second Half ends, Southampton 0, Brentford 2.
Corner, Southampton. Conceded by Mads Bech Sørensen.
Attempt missed. Michael Obafemi (Southampton) header from the centre of the box misses to the left. Assisted by Danny Ings with a cross.
Shane Long (Southampton) wins a free kick in the attacking half.
Foul by Shandon Baptiste (Brentford).
Foul by Jan Bednarek (Southampton).
Halil Dervisoglu (Brentford) wins a free kick in the defensive half.
Foul by James Ward-Prowse (Southampton).
Tariqe Fosu-Henry (Brentford) wins a free kick in the defensive half.
Attempt saved. Shane Long (Southampton) right footed shot from a difficult angle on the right is saved in the bottom right corner. Assisted by Kyle Walker-Peters.
Substitution, Southampton. Michael Obafemi replaces Nathan Tella.
Substitution, Southampton. Shane Long replaces Che Adams.
Hand ball by Danny Ings (Southampton).
Offside, Brentford. Rico Henry tries a through ball, but Halil Dervisoglu is caught offside.
Substitution, Brentford. Halil Dervisoglu replaces Marcus Forss.
Corner, Southampton. Conceded by Emiliano Marcondes.
Attempt blocked. Danny Ings (Southampton) right footed shot from outside the box is blocked.
Foul by Danny Ings (Southampton).
Bryan Mbeumo (Brentford) wins a free kick in the defensive half.