Atletico stunned the holders in the second-leg at Anfield to reach the quarterfinals.
Adrian told DAZN: "The best of the match was practically (Jan) Oblak and, in the end, Atlético made their match, they beat us in both matches and they had to pass because they deserved it."
But it left a "sour taste in the mouth" in the first days "for having lost the tie".
He added: "It was a game that had twenty-something shots on goal, two or three posts..."
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