The Reds progressed to their third Champions League semi-finals in the last five seasons after seeing off the Portuguese giants 6-4 on aggregate.
Klopp made seven changes to the side that drew 2-2 in the Premier League on Sunday against Manchester City, with the likes of Virgil Van Dijk, Andy Robertson, Trent-Alexander Arnold, Mohamed Salah and Sadio Mane all dropping to the bench.
That resulted in Liverpool conceding three goals at Anfield, although a healthy 3-1 lead from the first leg ensured they will go on to meet Villarreal in the last four.
"I made seven changes, the last line never played together like this, I decided that yesterday," Klopp told reporters after the game.
"So we had 15-20 minutes to try and put it right. The majority of times they did really well, I liked the way we played football, the only problem was when we lost the ball our protection was obviously not perfect.
"If you defend in a Champions League quarter-final it's about details. I didn't see the offside situations back, but it's part of defending to put the opponent offside.
"Tonight that didn't work out too well we have to admit, but that is my fault because I changed seven times.
"Benfica was still on fire and I respect that a lot. They scored really good goals, but it should not be as easy as it was tonight."
Liverpool are back in action against Manchester City again in the FA Cup semi-finals this weekend.
