The Madrid derby beckons in the last-8 of the Copa.
Despite holding a 1-0 lead from the first leg, it was Atletico who were the more adventurous side and they fired an early warning when Raul Garcia's sweetly struck volley cannoned off the crossbar after just ten minutes.
Atleti's persistent search for the crucial away goal to double their aggregate advantage paid off when they went ahead on 24 minutes. Raul Garcia's lob found Sergio Aguero, who dashed through in between two defenders and finished clinically past Cristian Alvarez with a powerful drive into the top of the goal.
Espanyol failed to respond despite needing three goals to save the tie, and Jose Antonio Reyes should have buried the contest on 33 minutes when Diego Costa's cross trickled to the winger at the far post, but his weak low shot towards the opposite bottom corner was cleared by Aldo Duscher.
The Blanc-i-Blau were saved again by another goal-line clearance when Didac headed away Aguro's clever chip. From the ensuing corner, El Kun did find the back of the net this time, but it was disallowed for offside.
In the final minutes of the first half, Aguero almost scored a stunning individual goal when he ran 50 yards with the ball, only to see his final effort from a tight angle smothered by Alvarez.
Espanyol came out all guns blazing in the second half and created two quickfire chances. Jesus Datolo's speculative cross bounced off the top of the bar with David De Gea stranded and from the follow up, Alvaro Vazquez saw his shot on the turn sail straight to the Atleti shot-stopper.
Espanyol coach Mauricio Pochettino sent in Luis Garcia on the hour mark to inject more attacking venom and within minutes, the veteran forward forced De Gea into a spectacular acrobatic save with a brilliantly struck volley. Seconds after that, Luis Garcia curled in an effort from 20 yards which crashed against the crossbar.
Atletico were starting to defend in numbers as they look to hit the Catalans on the break. Aguero led a swift counter-attack on 72 minutes and his searching low cross almost found Reyes, but Alvarez was quick off his line to clear the danger. Reyes again missed a glorious opportunity five minutes from time when he ran past two defenders, but his left-footed toe poke was easily collected by Alvarez.
Three minutes into injury time, Espanyol snatched a consolation equalizer when Luis Garcia arrowed in a sublime freekick into the top corner, leaving De Gea no chance.
But the goal came just a little too late as Atletico held on comfortably for a 2-1 aggregate win to set up a potential quarter-final clash with fierce rivals Real Madrid, who lead Levante 8-0 from the first leg.
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