After Sadio Mané doubled the Reds' lead, it looked like they would go on and get at least one more; that they didn't will be the source of some relief for Villarreal.
He hits a bouncing shot that Rulli punches clear, and when the ball is played back into the box, several Liverpool players are offside.
It was estimated that between 20,000 and 30,000 Frankfurt supporters were in attendance, the majority getting tickets in the Barcelona home end.
They have moments of footballing excellency.
Just like in the quarter-finals, we can expect to see more upsets in the Europa League semi-finals.
Villarreal must emulate Inter's class of '65 to go through Spanish soccer stats guru Mister Chip notes that Liverpool have only ever once been beaten in a European knockout tie after winning the first leg at home by two or more goals.