"We knew it could be a tough game and it was a tough game," said the Reds boss.
"They [Luton] worked really hard. We also worked hard but the only thing is when you score a goal you need to use your experience and control the game. But we conceded within three minutes and that was really disappointing."
The League One side looked more than capable of causing a huge cup upset for long periods of the contest and while the Reds boss acknowledged that his side did not play with their usual quality, he believes Liverpool will complete the job in hand in the replay a week on Tuesday.
"I think that it was really difficult because they were physical and it was a tough game, but in terms of the workrate I am happy with that," he said.
"In terms of the performance we can do better for sure. At least we have the chance to play another game at Anfield in the replay and I think it will be different."
