Adrian Lopez's injury-time goal gave Villarreal a 1-0 victory over Liverpool in the Europa League semi-final first leg.
Lopez collected Denis Suarez's unselfish cutback to slot home from close range in the second minute of added time, giving the La Liga side the advantage in the tie.
In an even affair, Joe Allen had an early shot from 12 yards saved by Sergio Asenjo, and the Villarreal goalkeeper was then at his best in the second half to tip Roberto Firmino's effort from 18 yards onto the post.
Simon Mignolet's superb late save from Cedric Bakambu kept the scores level until Lopez's late winner, and the two sides meet in the return leg on Thursday at Anfield, as Liverpool look for a fourth title in the competition.
Jurgen Klopp made three changes from the side that drew 2-2 with Newcastle on Saturday, leaving Daniel Sturridge on the bench as Philippe Coutinho, Nathaniel Clyne and Lucas Leiva were introduced.
It was Klopp's side who had the first clear-cut opportunity through Allen, whose low effort was saved well by Asenjo after Adam Lallana's deflected cross fell to the Wales international.
Former Tottenham striker Roberto Soldado then came close for the hosts, hitting his effort from an acute angle into the ground and a yard wide of goal after a quickly-taken free-kick.
Mignolet had to be at his best to beat away Tomas Pina's curling effort from the edge of the area, before Pina saw a second opportunity from a similar position well blocked by Dejan Lovren in the area.
Minutes before half-time, Soldado's deft effort from 20 yards went just wide of Mignolet's left-hand post as Liverpool went into the break goalless.
Villarreal came out strongest in the second half, and hit the corner of the post through Bakambu's near-post header a minute after the restart.
Firmino came closest to scoring for Klopp's side with 25 minutes remaining, taking James Milner's pass on the turn and hitting the near post via the outstretched hand of Asenjo.
Mignolet, who has come under criticism for his performances in recent weeks, looked to have kept the advantage with Liverpool with just moments remaining, superbly tipping wide Bakambu's placed shot with just two minutes remaining.
At the other end Alberto Moreno shot a yard high and wide of Asenjo's goal as Liverpool hit the hosts on the break, but it was Villarreal who broke the deadlock in the dying moments.
Kolo Toure got caught under a high diagonal into the box for Denis Suarez, allowing the Spaniard to bear down on goal, and the midfielder's unselfish pass enabled Lopez to slot into the empty net.