Liverpool’s ambitions of reaching their first European final in almost a decade suffered a blow as Villarreal netted an injury-time winner in the first leg.
After a first half of few chances, Cedric Bakambu’s header clipped the Reds upright shortly after the break.
The Reds looked set for a creditable draw in Spain until they switched off to allow substitute Adrian Lopez to tap in Denis Suarez’s low cross.
Despite the dramatic winner, the semi-final still remains delicately poised before next Thursday’s return leg at Anfield.
The winners will face either Spanish holders Sevilla or Ukrainian side Shakhtar Donetsk, who drew 2-2 in their first leg, in the Swiss city of Basel on 18 May.
EUROPA LEAGUE RESULTS
Shakt Donsk 2 – 2 Sevilla
Villarreal 1 – 0 Liverpool
