Luis Suarez’s second-half double in the first leg gave Barcelona a 2-1 lead in the tie after Fernando Torres opened the scoring for Atletico before being sent off in the first half.
That victory, however, was Barca’s only win in their last four matches in all competitions.
They are in the middle of their worst run in the league, with a draw and two defeats in their last three games, since Luis Enrique took charge in 2014.
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“I’m not focussing on Barcelona’s run, Atletico want to fight against the best teams and tomorrow is the day to do something big against Barcelona and stay in this competition which we love so much,” Gabi told a news conference.
“The key is to control our emotions, play intelligently, we have known how to play these types of games for the last three or four years.”
Gabi also said that Lionel Messi's run of four club matches in all competitions without a goal would not make it any easier to cope with the Argentine.
"It's difficult to prepare yourself to play against Messi, I'm prepared to play against Barcelona," said the midfielder.
"Messi tips the balance, with support we can stop him, although we know it will be difficult."
Atletico knocked Barcelona out at the quarter-final stage in 2014 by winning the second leg at the Vicente Calderon 1-0, but coach Diego Simeone said the past would count for nothing on Wednesday.
“What happened before remains in the past,” he told a news conference.
“During the game similar situations to before can occur, but what happened before will not influence us before the game.”
The Argentine coach also said the support of the home crowd would not give his side an advantage.
“The game will be played by us,” he said.
“The game will be won by scoring one more goal than the opponent. The enthusiasm and atmosphere around us is fantastic but the Barcelona players will not be surprised by it.
"We have to do our own thing, the fans will respond as they always do and we will be on the pitch looking to qualify for the semi-finals.”
(Reporting by Richard Martin; Editing by Toby Davis)
