Atlético Madrid shocked Barcelona with four goals in the first half to win the first leg of their Copa del Rey semifinal 4-0 at the Metropolitano stadium on Thursday.

A disastrous first 45 minutes for the visitors started when Joan García tried to control Eric García's harmless-looking pass but the ball went underneath his foot outside the six-yard box.

García ran and dived to try to keep the ball from crossing the line, but didn't make it back in time. He swatted the ball back into play -- and Atletico forward Ademola Lookman then sent it into the net -- but the ball had earlier crossed the line.

Antoine Griezmann gave Atlético a 2-0 lead by scoring in the 14th, Lookman added a third in the 33rd and Julián Álvarez got a fourth goal in first-half stoppage time.

Barcelona prevented further damage in the second half but saw defender Eric García sent off for a rash challenge in the 85th minute. The LaLiga leaders also had a Pau Cubarsí goal ruled out early in the second half after a lengthy check from the video assistant referee.

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Joan García had made a fine early save to deny Giuliano Simeone at point-blank range, but was then culpable for gifting Atletico the lead in the seventh minute.

Atletico then doubled their advantage following a flowing move, with Griezmann sweeping the ball into the bottom corner from the right.

Barcelona almost reduced the deficit in the 19th minute when Fermín López crashed a volley against the crossbar following a corner.

After Álvarez saw his goalbound shot hooked off the line by Barcelona defender Jules Koundé and Griezmann fired over, Atlético soon scored a third. Simeone charged down the left and picked out Álvarez, who flicked a first-time pass on for Lookman to drill past Joan García.

Atletico's frontline remained too hot to handle and added a fourth in first-half stoppage time when Álvarez drilled in a cutback from Lookman.

Barcelona thought they had pulled a goal back in the 52nd minute when Cubarsí lashed the ball in after it had bounced through a crowded penalty area following a free kick.

There was a lengthy VAR review -- which took around eight minutes -- before the goal was ruled out for an offside.

With five minutes left, Eric García had initially been shown a yellow card for a rash challenge on Baena who would have been clean through on goal -- but after the referee was advised to take another look by VAR, it was upgraded to a red.

After tempers flared out on the touchline with a melee between players and coaching staff, which was eventually calmed down, Ferran Torres then headed wide from a corner -- which about summed up Barcelona's forgettable evening.

The Associated Press and PA contributed to this report.