Arsene Wenger offered no excuses after a much-changed Arsenal were beaten 2-0 by Southampton in the quarter-finals of the EFL Cup on Wednesday.
Only Mohamed Elneny maintained his place in the starting XI as the Gunners were outplayed at the Emirates.
Jordy Clasie and Ryan Bertrand scored the goals in the first half for Saints, who also made eight changes from their weekend win over Everton.
"There are no excuses and we can only say Southampton were better than us," said Wenger.
"We had a disappointing performance, especially in the first half. We were not good enough defensively and we gave cheap goals away.
We were weak in some departments and we were punished for that.
"It's one of those nights where you can play for two hours and not score. We were weak in some departments and we were punished for that.
"We were not incisive enough. They defended deep and were sharper and fitter than us. With a two-goal advantage they defended very well."
Asked whether he had any regrets over making such wholesale changes, Wenger said: "I regret the way the game went.
"We have played well until now and when you look at the players who didn't play tonight, they were on the edge physically.
"When you look at the team we had, I don't think that was the problem. We didn't have the right urgency from the beginning of the game."
Even the one player who did keep their place in the line-up had to be replaced before half-time, with Wenger revealing Elneny was "sick before the game".
"He said he was well enough but I could see after 10 minutes he wasn't right. He has a stomach problem," added the Arsenal boss.