While the London club have exuded an air of confidence ahead of the Nou Camp clash, the Portugal international believes that Barca's 2-1 defeat to Real Madrid at the weekend could play in the Catalans' favour.
"Barcelona's defeat against Real Madrid could have some effect on the game on Tuesday, but it's a double-edged sword because after practically losing the league, their challenge is Europe and they will come out with even more motivation," Meireles told Goal.com.
"The game at Camp Nou is a final for us. It's not easy to knock out Barcelona but first blood went to us and now we will have to play even more perfectly on Tuesday."
The winners of the highly-anticipated clash will meet either Real Madrid or Bayern Munich in the final in Germany.