Ralph Hasenhüttl felt Southampton were the better team in defeat at Tottenham, but admitted his side could not be surprised to lose given the way they defended in the closing stages.
Saints trailed to an early own goal from Jack Stephens, but rallied to score twice through Shane Long and Danny Ings – the second goal coming just 18 minutes from time.
The visitors had outplayed their hosts, but Spurs found some momentum after Lucas Moura levelled the FA Cup fourth-round replay, and Son Heung-Min’s late penalty booked their place in the last 16.
“I think we played better than they did and found a good balance, created chances, but we scored only one goal after the break,” Hasenhüttl said.
“This should still be enough to win such a game, but it’s clear that in the end they will try everything and the way they scored was too easy.
“We gave them too much space in the centre, didn’t close the gaps and they showed they have the quality to kill you.
“If you stop defending in the way that we normally do for the last 15 minutes, you don’t have to be surprised that you lose such a game.
“It doesn’t matter that you play a good game and go 2-1 up – it wasn’t good enough to win here. We were close, but not good enough.
“We invested a lot, tried to go with the best team to go to the next round, but we didn’t do it.”