The problem with assuming a Europa League winner with Sevilla is bound to conquer the continent is that there is more than one of them. Unai Emery can seem the king of Europe, but a defending champion has one foot in the Europa Conference League final. Rather than Emery’s fifth European trophy, it could be Jose Luis Mendilibar’s second in as many years after, courtesy of Ayoub El Kaabi’s hat-trick, Olympiacos stormed Villa Park.

Aston Villa may retain hope of two trips to Athens this month, for the final as well as the semi-final second leg, but they came Acropolis in Birmingham.

After penalties brought them to this stage, they could rue two more: the one Douglas Luiz conceded and the one he missed.

Villa’s first European semi-final for 42 years was a classic, but one they could regret, their defensive frailties allied with different types of misfortune for Olympiacos’ third and fourth goals. A historic occasion may lead to a landmark outcome if Olympiacos become the first Greek club to win a European trophy.

A night when Villa mustered one comeback, with Moussa Diaby creating one goal and scoring another either side of half-time, leaves them needing another.

Frenetic entertainment left Villa, in their first European campaign for 14 years, looking naive, despite Emery’s extensive experience. They can play a game of brinkmanship with their high defensive line but El Kaabi breached it twice in 14 first-half minutes. Olympiacos were cutting on the counterattack. Emery lost out to a fellow Basque; indeed, a more recent Sevilla Europa League winner. If Mendilibar had a reputation as a kind of Spanish Tony Pulis, he is shrugging it off to become a European specialist, parachuted in mid-season again, having another immediate impact.

For Villa, having won all six European home games this season, as the favourites for the competition, this represented an unwanted shock. The atmosphere was electric, Villa Park a sea of claret and blue. Yet Olympiacos were not to be intimidated. Enterprising and excellent, they scored four and could have got more, with Kostas Fortounis whistling a shot over and Chiquinho drawing a fine save from Robin Olsen.

And any sense Villa could do without Emi Martinez was misplaced. Not that Olsen was particularly culpable for any of the goals and the Swede was luckless for the fourth, when Santiago Hezze’s shot took a huge deflection off the back of Ezri Konsa. They could have done with a penalty specialist for the third, though, but Martinez’s antics in the shootout in Lille, earning him a second yellow card but not a red, meant the World Cup winner was missing. Perhaps a goalkeeper of his brilliance might have conjured something special, though; with Villa so open, they required rescuing.

It hardly helped that, lacking Youri Tielemans, they were short of midfielders. Emery picked a more attack-minded team than usual and a six-goal thriller was the consequence. El Kaabi’s treble took him to 31 for the season, 13 of them in Europe. The menacing Moroccan is now the joint top scorer in the Conference League, despite spending autumn in the Europa League.

He pounced when Olympiacos twice sprang the offside trap, with Villa’s full-backs both found faulty. His first goal was chalked off then awarded, the initial verdict of offside overturned by the VAR. The watching owner Evangelos Marinakis presumably did not complain about this decision. As Chiquinho flicked the ball forwards, Matty Cash was caught behind the rest of the defence, rendering the goal legitimate. Then Daniel Podence, a loanee from the West Midlands, chipped the ball forward, El Kaabi headed it down and dispatched a half-volley. His was a magnificent display, a No 9 with purpose and presence, power and pace.

Villa had a threat of their own. They had already seen a Leon Bailey strike disallowed for a foul by Clement Lenglet and were denied a spot kick when the Jamaican seemed to be fouled by Francisco Ortega.

They pulled level with two quality strikes. The first was a typical Villa goal, Ollie Watkins making a diagonal run to meet Diaby’s through pass and arrow in a shot. Emery signalled to calm down. No one did and Diaby continued to exert an impact, racing on to Bailey’s pass, finishing from an acute angle, with the aid of a misjudgement by Kostas Tzolakis, who left a gap at his near post as he anticipated a cross.

Yet they only had parity for four minutes. Then Panagiotis Retsis’s header on to the raised elbow of Douglas Luiz. It was an unnatural position but the Brazilian was barely a yard away. El Kaabi sent Olsen the wrong way. Then Hezze’s strike put Olympiacos two goals to the good again.

Villa’s response was forceful but the outcome added to a sense of wastefulness. David Carmo fouled the substitute Jhon Duran but the usually reliable Douglas Luiz clipped the post with his spot kick.

If Villa’s capacity to give gifts to Greeks could prove their undoing, they may wish Sevilla had not sacked Mendilibar, months after he led them to continental glory. Now instead of Emery, he could be the Spaniard adding the Conference League to the Europa League.