Angel Correa and Marcos Llorente registered a brace each as Atletico Madrid destroyed basement side Eibar to extend their lead at the top of La Liga to four points.
Atleti were without the injured Luis Suarez and Joao Felix and in their absence, the hosts really struggled to create chances for the majority of the opening period.
But after an anxious 41 minutes, Correa stepped up to score twice in two minutes before the interval to set Diego Simeone's side on their way. The 26-year-old was left unmarked from Kieran Trippier's corner delivery to slot home unmarked at the near post to break the deadlock, before grabbing his double after a lovely turn and composed finish from Yannick Carrasco's cross.
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Two more goals seven minutes after the restart put the tie to bed as the floodgates opened. Eibar's defence was caught square as Saul's long ball over the top released Carrasco who knocked it past the onrushing goalkeeper and tapped into an empty net. Llorente got on the scoresheet moments later with a first-time finish as goalscorer Correa turned provider.
Carrasco was involved again as the hosts made it five with more 20 minutes still remaining, the Belgian pulling the ball back to Llorente whose shot nestled in the far corner for his 12th league goal this season.
And that wrapped up a morale-boosting triumph for Atletico Madrid, who move to 70 points, four above Real Madrid ahead of Los Blancos' away game to Getafe later on Sunday.
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After just one win in four games, this was a much-needed victory for Atletico Madrid. Simeone's side has really been feeling the heat in recent weeks as a stuttering run of form saw Real Madrid and Barcelona - and even outsiders Sevilla - close in.
But Atleti have triumphed in the first of eight cup finals as the La Liga title races nears its climax. And they did it in some style, earning the kind of convincing victory that Simeone would have been craving. It sets them up nicely as they close in on a first league title in seven years. They now turn their attention to a home match with Huesca on Thursday.
MAN OF THE MATCH - Yannick Carrasco (Atletico Madrid)
There wasn't much to choose between Correa, Carrasco and Llorente, all of whom performed close to their best. But with two assists as well as goal, Carrasco just edged it.
Atletico Madrid: Oblak 6, Trippier 7, Gimenez 6, Savic 6, Lodi 8, Saul 7, Koke 7, Herrera 7, Carrasco 9, Correa 9, Llorente 9.. subs: Vitolo 5, Torreira 5, Kondogbia 5, Dembele 5, Felipe 5.
Eibar: Dmitrovic 4, Dufur 4, Burgos 4, Arbilla 5, Cote 4, Atienza 4, Pozo 5, Alvarez 4, Garcia 4, Rodrigues 4, Kike 5.. subs: Inui 5, Rafa 5, Gonzalez 5, Oliveira 5, Recio 5.
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42' - GOAL! Atletico Madrid 1-0 Eibar (Angel Correa): Correa with the breakthrough! He bags his fifth goal of the season - and it's a huge one! Trippier's corner delivery is flicked on by Herrera and Correa is free at the back post to bundle it over the line!
44' - GOAL! Atletico Madrid 2-0 Eibar (Angel Correa): Two goals in three minutes and Atleti are cruising! There's that diagonal ball that has caused Eibar trouble all afternoon as Lodi is left unmarked on the flank. He rolls it to Carrasco and he feeds Correa. He takes out Arbilla with a lovely turn before sliding it home for his brace.
49' - GOAL! Atletico Madrid 3-0 Eibar (Yannick Carrasco): The visiting defence is caught square from Saul's simple long ball over the top. Carrasco nudges it past the onrushing goalkeeper before finishing into an empty net. That should do it!
53' - GOAL! Atletico Madrid 4-0 Eibar (Marcos Llorente): Atleti are tearing the visitors apart! The goal comes from the left once more, as Lodi is found in space - again. Correa takes over, rolling a ball into space for Llorente and he finishes with a first-time side-footed shot.
68' - GOAL! Atletico Madrid 5-0 Eibar (Marcos Llorente): Llorente at the double! It's all too easy for Atleti. It's worked down the left flank, with Carrasco pulling it back to centre. Llorente is found in space inside the penalty area and he keeps his composure to rifle a shot past the helpless Dmitrovic.
Atletico Madrid are now unbeaten in 17 of their last 18 matches against Eibar in all competitions.
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