Atletico Madrid failed to beat second division's Celta Vigo at home in the Vicente Calderon Stadium Thursday night, complicating their progress to the Spanish King's Cup semifinals.
Quique Sanchez Flores' side, which beat Recreativo Huelva 5-1 in the Calderon a week ago, was clear favorite to do the same to Celta.
Although Quique put his strongest side onto the pitch, Atletico was stunned on just two minutes after Trashorras gave the visitors the lead.
New signing Thiago Cardoso leveled for Atletico nine minutes later, but if anyone was expecting that to be the start of an Atletico revival, they were in for a disappointment.
Celta played the better football throughout the match and limited the options of Atletico strikers Diego Forlan and Kun Aguero.
Meanwhile, Racing Santander will take a narrow 2-1 lead to Pamplona next week after a tough win against Osasuna.
Although Sergio Canales failed to score this time for his side, Racing looked to be cruising after second half goals from Gustavo Colsa and Papa Diop.
Walter Pandiani scored a vital away goal for Osasuna after 88 minutes to leave his side needing to score just once in the return leg to book a place in the last four.