West Ham were beaten in the first leg of their Europa League Round of 16 encounter, as Sevilla won 1-0 in Spain.
The Liga side have been in exceptional form in La Liga and are currently second in the table.
They are the most successful team in the competition’s history, meaning this was always going to be a stern test for the Irons.
And they were beaten on Thursday night, with the decisive goal coming from Munir just before the hour mark.
It was a poor goal for the Irons to concede as the Hammers left Munir unmarked, and allowed him to power a half-volley into the bottom corner after Marcos Acuna’s free-kick.
In the first-half, the Irons had a couple of chances to take the lead in Spain, with the big chance falling to Nikola Vlasic, who had the opportunity to score a free header at close-range. His diving header, though, was well saved by the Sevilla goalkeeper.
The Hammers were perhaps lucky not to fall 2-0 down when Lucas Ocampos was given a brilliant chance to score for Sevilla after Craig Dawson surrendered possession, but his shot whistled past the post.
Manuel Lanzini also had an opportunity to equalise, with his shot from 10 yards out well blocked by Jesus Navas.
If the Hammers are to go through, they will have to score twice in east London in the second leg.