Blues boss Guus Hiddink admitted he was worried his team were going out after going in at half-time 2-0 down.
"You can kill the game in the first half-hour by not conceding, but not by sitting back, with your backs in the goal - then you ask for problems, and we were worried.
"It was a matter of having too much respect so we got a little bit angry and the team reacted. That's what I liked in the second half."
Liverpool manager Rafael Benitez insisted everyone associated with the Reds could hold their heads high after tonight's display.
"We are disappointed because we scored four goals away from home and this game was unbelievable, and I'm really proud of the players and fans because they were pushing the team all the time," he told ITV1.
"I thought we played a really good game."
Benitez admitted he thought the upset was on at half-time and put the eventual heartbreak down to errors.
"When we scored the second goal I had confidence," he added.
"When they scored their first goal I thought we could still do it, but when you talk about Chelsea they have top-class players and they punish you when you make a mistake."
Two-goal hero Frank Lampard hailed Chelsea's character after they marched into the Champions League semi-finals following an amazing 4-4 draw with Liverpool.
On a sensational night at Stamford Bridge, Fabio Aurelio and Xabi Alonso put the Reds on the brink of a great comeback at half-time after the Londoners' 3-1 first-leg victory. But an own goal from Jose Reina plus strikes from Alex and Lampard appeared to have ended the tie, although Lucas and Dirk Kuyt restored hope before Lampard's last-gasp clincher.
Lampard, who admitted he was "in bits", told ITV1: "It was a great game of football.
"We made it hard for ourselves and Liverpool are a fantastic team. But it's a great night, we're through."
The England midfielder added: "Our character at half-time, to turn it around, says a lot about the players."
Of the forthcoming last-four clash with in-form Barcelona, Drogba said: "It's going to be difficult but if we want to win the Champions League we have to play these big teams."