Jurgen Klopp credited the contributions of his substitutes for Liverpool's comeback victory over Leicester.
The Reds moved into the last four of the Carabao Cup after fighting back from 3-1 down at the break to eventually win 5-4 on penalties against a strong Foxes lineup from Brendan Rodgers.
Klopp introduced Diogo Jota, Ibrahima Konate and James Milner at half time before swapping captain Jordan Henderson for the outstanding Naby Keita near the hour mark.
The Reds boss explained what he told his charges at the break before they went on to fight back with a stoppage-time equaliser from Takumi Minamino after Jota had made it 3-2.
“I'm really really happy, really happy with the performance, with the spirit, the mentality," Klopp said.
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"In a lot of moments with the football it was difficult for us in the first half as we had to make a lot of changes.
"I think Neco Williams can play in an offensive role but together with Conor Bradley [at right-back] it didn't work out that well even though Conor is an incredible talent, I love the boy to bits.
"We had to make changes in the second half, Tyler Morton because of the yellow card and Billy Koumetio because Ibou (Konate) was there and could play 45 minutes.
"I wanted to make sure he didn't start as we would have let him pay a lot longer.
"In the first half when we played the right football we were good but when we played in their formation it was not good, they had counter-attacks and scored easy goals.
"At half-time we told the boys 'I like the game apart from the mistakes we made around the goal and improve in a few moments. We should play around their formation, to play in the half-spaces more.'
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"The changes helped of course, when you can bring in Jota in the shape he is in, having Millie at No.6 [in midfield] was clear we wouldn't struggle for mentality any more and Naby when he came on, oh what a game he played.
"The boys were just outstanding. I really liked it a lot."
On the performance of shootout hero Caoimhin Kelleher, who saved twice from Luke Thomas and Ryan Bertrand, Klopp added: "Caoimhin, not only with the penalty saves but the save with Albrighton he saved our lives. We are in the semis - great.
“Of course it is important, but he is an outstanding goalkeeper, I don't want to say any more. He is a talent but he is an outstanding goalie, good with his feet, good game understanding.
"It is nice. It is not the first time he was part of these spectacular games, against Arsenal it was similar but this is a step forward and he saved our lives, he was really helpful tonight."
Asked about the performance of Minamino, Klopp said: “Top goal, top performance.
"When you change that much it is not 100 per cent fair as they have to play absolutely their top game, but he played a really good game.
"From a tactical point of view he was outstanding and it was great for him to score that goal in the best possible moment.
"He deserved his goal for all the things he did tonight and all the things he did in the last few months."
