The loss at the Cornella-El Prat was Atletico's first of the season, but the Belgium centre-back, who made his debut in the clash, is confident that the capital outfit will respond.
"You cannot win them all and we know that. We did the best that we could and we had chances to draw or win the game," Alderweireld told reporters at a press conference.
"We have to continue on. Now we think towards three points in the Champions League, to forget the defeat against Espanyol."
Alderweireld joined Atletico from Ajax in the summer, but had to wait six weeks to make his first appearance for the Spanish outfit.