The Argentine midfielder believes the Catalans have the psychological edge ahead of Wednesday night's Clasico clash - as well as the world's best player, Messi, on their side
Barca won the first match 2-1 at the Santiago Bernabeu last week and will advance to the last four of the competition by avoiding defeat on Wednesday, thereby gaining some revenge for its loss to Jose Mourinho's men in the final of last season's Copa del Rey.
That match remains the only disappointment for Barca boss Pep Guardiola in the Clasico since taking over at Camp Nou in the summer of 2008, and the only time Mourinho has tasted success in the famous fixture, too.
"We have the measure of Madrid," Mascherano told Goal.com in an exclusive interview. "But that doesn't always guarantee success and we are still not in the semi-finals of the cup," he added with a note of caution.
"The tie against Madrid isn't won yet, but we are optimistic; we have a good advantage from the first leg but it is no good being over-confident and we know Wednesday will be a harder match than the one at the Bernabeu."
Mascherano says Sunday's sublime showing at Malaga, where Barca beat the Andalusians 4-1, will give the Catalans confidence for the latest Clasico clash and adds that his side depend on themselves on Wednesday.
"The three points we won at Malaga on Sunday in the league will give us more energy for the cup match," he said. "We are working well and now we have to finish the job at home.
"We know that Madrid will give us a difficult match because they are obliged to come out and win if they want to get to the semi-finals, but this game depends on us and if we manage the situation well, we will be in the next round."
The Argentine midfielder, who has been utilized in defense by Guardiola on numerous occasions over the last two seasons, claims he is looking forward to what he describes as one of the world's finest fixtures.
"The atmosphere is guaranteed and the passion as well," he enthused. "Nobody can doubt that this is one of the best games in world football today."
And aside from their first-leg lead, the former Liverpool star claims Barca have one more big advantage over their biggest rivals: Lionel Messi.
"For me there is no doubt," he stated. "Leo Messi is the best player in the world whether he scores three goals in a game or whether he doesn't score at all. With him we have a plus point that no other team can count on."
Follow GOAL.COM USA on