The defender believes Barcelona deserved to go through to the semi-final to set up another clasico but insists that Los Blancos will be hurt by the loss of their skipper
The Blaugrana came out 6-4 aggregate victors after a pulsating encounter with Malaga which means they will face Jose Mourinho's men in the last four.
But the 25-year-old admits that they were matched all the way by Manuel Pellegrini's side.
"It was not easy at all. We had to work hard and keep the ball, although at times the game had been end-to-end. Even so, the result is fair," he told reporters.
"We knew it would be difficult. We came here needing to win, and both teams have played a great game.
"From the position I play, I didn't think I would score so early. But I'm very happy to have qualified."
Thursday's result has set up a mouth-watering clash with Real Madrid which is scheduled to be played on January 29, and Pique thinks the loss of their skipper, who fractured a finger against Valencia, is a big blow to Los Blancos.
He said: "Casillas is the captain and an emblem of Real Madrid. He has shown his quality over many years.
"His absence will be felt: not because of Adan, who is a great keeper, but because of the fact that Madrid will be without their captain."
On the contrary, Barcelona's assistant coach Jordi Roura has shifted attention away from the upcoming match against the Catalan club's arch-rivals.
He added: "I prefer not to talk about Real Madrid, we have to play Osasuna first."
Malaga's Spanish winger Joaquin conceded that it was only a matter of time before Barca breached Manuel Pellegrini side's backline.
Joaquin said: "We hung in there as long as we could, but Barca are an extraordinary team, and they have the best player in the world."