Southampton Puel off a shock to dump Gunners out of Cup
Southampton outclassed a much-changed Arsenal side to seal a comfortable victory at the Emirates Stadium and secure an League Cup semi-final berth for the first time in 29 years.
Arsene Wenger made 10 changes to his team from Sunday's win over Bournemouth but those who came into the starting line-up were found wanting as Saints were good value for their 2-0 win.
The visitors, showing eight changes of their own from the weekend, eased through as Jordy Clasie's first goal for the club was followed up by a smart Ryan Bertrand finish as Claude Puel's men wrapped up the win before half-time.
Saints have now won three of their last five meetings with the Gunners, who finish their usual troublesome month of November with just a single victory to their name.
After a slow start, Bertrand's cross fell to Sofiane Boufal and his shot was blocked by Rob Holding into the path of Clasie, who finished well from the edge of the box to give Southampton a 13th-minute lead.
With so many alterations, the hosts were struggling to find any sort of tempo and Saints goalkeeper Fraser Forster went untested throughout the first half.
Saints looked dangerous when they could break, although Shane Long was often too isolated to punish the numerous lapses in concentration that saw Arsenal yield possession.
But they did take advantage when the recalled Carl Jenkinson was caught on the ball seven minutes before the break, Steve Davis driving forward and playing in Boufal, whose cross was controlled and slotted home by Bertrand.
Wenger's night got worse before the break as Mohamed Elneny, the only survivor from Sunday's win, was forced off through injury.
Arsenal came out after the interval with much more intent, with Lucas Perez and Aaron Ramsey at least working Forster early on in the second half.
At the other end, Emiliano Martinez, having signed a new deal with the Gunners, struggled to keep out Long's arrowed effort as it almost passed through him to put Saints further ahead.
Granit Xhaka, who came on to replace Elneny, rasped a free-kick which Forster also dealt with, before Boufal danced through the Arsenal defence only to see his shot deflected behind.
From the resulting corner, Sam McQueen drove an effort just wide while Martinez and Saints skipper Virgil van Dijk reeled after colliding in air.
Alex Oxlade-Chamberlain and Ainsley Maitland-Niles were introduced by Wenger just after the hour mark, with Perez having a shot deflected behind.
Long could have made things worse but he shot wide when through on goal with substitute Josh Sims also testing Martinez late on.
But by then the game was already sewn up, with Southampton the side advancing to the final four, as jeers from the home fans greeted the final whistle.