After winning 3-1 at Anfield in the first leg, Chelsea were expected to cruise through but twice they were within one goal of surrendering that lead as Liverpool made a heroic bid for victory. It wasn't until Frank Lampard scored his second goal in the last minute that the Blues could finally relax.
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"Barcelona have skilful players and they know how to handle the pace of the game. They always like to play an advanced, attacking game," Hiddink said.
"If you give teams who are very skilful too much space, they know how to handle it and go into that space. Then you are in for a very difficult match.
"It is difficult to play them because they are a top team, but it is one of those beautiful games at the end of the season."
Chelsea's cause won't be helped by the absence of Ashley Cole after he picked up a booking that triggers a one-match ban. With Paulo Ferreira injured, Hiddink has no experienced cover for the England left-back.
Hiddink will also have to spend time working out a way to restore Czech goalkeeper Petr Cech's shattered confidence.
After conceding three goals against Bolton on Saturday, Cech looked a nervous wreck and was caught completely out of position by Fabio Aurelio's clever first half free-kick.
Hiddink admitted Cech's morale is low but refused to consider dropping him for Saturday's FA Cup semi-final against Arsenal.
"Petr is very intelligent and self-critical. He wasn't happy with his performance against Bolton. He knows he had a difficult time and also against Liverpool you could see there were times when he didn't have full confidence," Hiddink said.
"But I think a goalie once in a while has a right not to have a big performance. We will think about the situation but if a player is playing badly it is not always the reason to make a change."
Liverpool had taken the lead when Aurelio deceived Cech by driving in a low free-kick to the near post instead of crossing to the far post as the Chelsea keeper expected.
Cech was rooted to the spot as Aurelio's shot flashed into the net and he was helpless again when Xabi Alonso picked himself up to drive home a penalty after Branislav Ivanovic fouled the Spaniard.
But Hiddink read the riot act to his players at half-time and the transformation was instant. Liverpool 'keeper Jose Reina pushed Didier Drogba's close-range finish into his own net, then Alex lashed in a blistering free-kick that gave Reina no chance.
Lampard looked to have won it when he converted Didier Drogba's cross but Liverpool refused to accept defeat and Lucas pulled one back with a deflected effort in the 81st minute.
That seemed to be no more than a consolation, yet Dirk Kuyt headed in Albert Riera's cross two minutes later before Lampard's curler finally finished the thriller.
"We talked to them, my colleagues talked to them and sometimes you lose a bit of your temper," Hiddink said. "But they reacted and they also knew the first half was not okay.
"We were angry because we didn't start as we planned. You cannot give them a lot of space but we did. We dropped back too much and looked for safety.
"Tactically but also mentally we said to each other, that it was not the way we would start the second half. That's why I like to work with this team, it reacts.
"We knew that we could score and happily we did rather early after the beginning of the second half.
"It was very dramatic. One moment you think you are down and then the team reacts and then you are up before you are down again. It was a case of being in the game then almost being out of it."