The competition has long been a domain dominated by City, who have won the Cup on six occasions since 2014, but for the second time in as many seasons, they were knocked out before the semifinals.
For only the third time in Pep Guardiola’s tenure as City boss, and the first time since 2018, his side did not even manage a shot on target.
“That’s the reason why we were not good,” he told Sky Sports when asked about that statistic.
Southampton struck twice before the half-hour mark and defended well to limit City’s opportunities going forward despite only having 28% of the possession.
Guardiola was forthright in his analysis of his side’s performance, telling BBC Radio 5 Live: “The better team won. We didn’t play good, we didn’t play well in the beginning. There are many games you can start not good and overcome and we didn’t do it.
“When you are not prepared to play this game you arrive one inch late and don’t score a goal. When you are prepared you score the goal.
“Today was a bad night, the opponent was better so we have to congratulate them. To win games you have to deserve it and tonight we didn’t deserve it.”
Guardiola had named a strong side with Joao Cancelo, Jack Grealish, Ilkay Gundogan and Kalvin Phillips among the starters, yet apart from an early shot dragged wide by midfielder Gundogan they made little impression on the game.
Guardiola’s sentiments were echoed by Gundogan, who was disappointed with his side’s performance.
“It’s definitely not what we wanted,” the German told Sky Sports.
“We had hopes of going through in the Carabao Cup but with that [performance] there was no chance. It was not enough from us.
“With the ball we made a lot of mistakes, missed a lot of passes, gave them the ball too easily and that resulted in the two goals.
“Today we were not good enough to create chances, not good enough to score a goal. The mix of the performance from all the team gives this result.”
City will need to improve on Saturday for their next game, a Premier League derby away to neighbours Manchester United, who have won their last eight competitive games.