Diego Ribas' stunning goal gave the Rojiblancos the lead at Camp Nou in the first leg of the quarter-final, but Neymar's eventual equaliser ensured that the clash ended 1-1.
The capital club have played Barcelona four times this season, drawing each time, but the midfielder has insisted that his team-mates will give their best performance against the Catalans on Wednesday.
"This is best time of our lives," Gabi told reporters on Tuesday. "We are not tired. We want to compete at our best level, to give our best.
"The key to the match will be remaining concentrated throughout the 90 minutes. It’s not easy to stop players like them.
"We are looking to be as concentrated as possible. Our minds are not focused on drawing this game. We haven’t even thought about [a penalty shootout]."
Gabi also hinted that home support could give Diego Simeone's men the advantage and has called on fans to get behind the team at the Vicente Calderon.
"The fans will be very important for us tomorrow,” he added. “We made people believe and I think we are going to see Atletico's best from now.
"It’s going to be an important match for the club’s history and we want our fans to enjoy it."