Liverpool were hit with a late sucker blow at El Madrigal as sub Adrian Lopez gave Villarreal a precious advantage to take to Anfield.
Jurgen Klopp’s side were cautious Â– as they had been in Dortmund in the last four Â– and appeared destined to take a scoreless draw home from Spain before Lopez tapped in from close range two minutes into stoppage time.
In truth, it was harsh on Liverpool who had marshalled their hosts well for long spells and given up very few decent chances.
The La Liga side were elated with their late salvo and will now head to Merseyside in upbeat mood for the return encounter.
It could have been so different for Liverpool had Joe Allen netted a golden chance inside five minutes.
A low cross from the right found Allen on the penalty spot but his first-time shot was straight at Sergio Asenjo.
On ten minutes, former Spurs forward Roberto Soldado controlled a quick free kick from Bruno Soriano only to fire an angled shot wide of the post.
Five minutes from the break Philippe Coutinho Â– subbed off feeling unwell at half time Â– blasted over a shot from 20-yards while at the other end Soldado’s curling effort from outside the box went the wrong side of Simon Mignolet’s post.
Overall the first 45 minutes was a tame affair with neither side able to fashion any genuine chances.
Within seconds of the restart Cedric Bakambu steered a header into the side netting from a corner as Villarreal sought to up the tempo.
Liverpool still had all the answers and midway through the second period it was the Reds that almost made the breakthrough.
James Milner fed the ball into Roberto Firmino and he swivelled inside the penalty area before blasting low at the target with Asenjo doing well to tip the ball onto to his near post.
From there the game seemed to meander towards an inevitable stalemate before Bakambu sparked a late flurry of activity.
He got away from the Liverpool cover and his shot from 20-yards forced Mignolet to turn behind for a corner as the game entered added time.
After a couple of set pieces, Liverpool swarmed forward and Alberto Moreno blasted just over from inside the box.
With time almost up, Suarez burst into the box and squared the ball unselfishly past Mignolet to give Lopez the easiest of finishes.
It was a priceless goal and the Yellow Submarine are now in much more peaceful waters going to Anfield than appeared likely for much of the first leg.