First-half goals by Joan Torrents, Pascual Medina, Marlone Foubert and Rodrigo Alonso stunned the home crowd at Leigh Sports Village and left the Reds facing a heavy defeat to follow up the opening Group F win at Young Boys.
The challenge must have been to win the second half, and the boys achieved this, thanks to a header by Alvaro Fernandez.
Villarreal dominated possession from the first whistle and soon went in front, with only five minutes on the clock. A through ball was allowed to find Medina and, although his effort came back off a post, Torrents was on hand to supply a simple finish into the unguarded net.