Liverpool boss Jurgen Klopp admits Sheffield United pushed them hard for Thursday night's 3-1 win.
The Reds won thanks to goals Alexis Mac Allister and Cody Gakpo in the second-half.
Klopp said: "We had to dig very deep, but that is normal. Our attitude was good, the football was not great in a lot of moments.
"We saw how quick passes can change the game after 60 minutes, Robertson down the line, bam bam bam. Then Macca's goal [Alexis Mac Allister] was the complete game changer, and it's a wonderful goal for 3-1 as well. The first goal, Darwin does it by himself."
On Sheffield United, he said: "They could have scored after 20 seconds, Caoimhin [Kelleher] makes a great save. Sheffield United played how they wanted for 90 minutes. It is difficult, but we could do better, and we did to get the win."
On Mac Allister, he added: "He is a really good player, in the first half he was playing six but we knew we could move him slightly higher. Then he scores this kind of goal, the two biggest screamers of the season have come from him. Then the free-kick directly after - absolutely insane, what a player."
