Ayoub El Kaabi scored his first hat-trick in European competition to lead Olympiakos to a 4-2 victory over Aston Villa in the first leg of the UEFA Europa Conference League semi-finals.Both goalkeepers were forced into early stops, before Leon Bailey thought he had given Aston Villa a ninth-minute lead in the club’s first European semi-final in 42 years. However, the Jamaican’s celebrations were short lived after the officials ruled there had been a foul in the build-up. The Villa faithful experienced more frustration when El Kaabi produced a thumping finish to put Olympiacos in front after replays confirmed Matty Cash had played the striker onside. El Kaabi wasted little time in giving the Greek contingent another goal to celebrate, latching onto Daniel Podence’s neat through pass, before slotting under Robin Olsen’s despairing dive.As the contest entered first-half stoppage time, Ollie Watkins gave his side a much-needed foothold in the tie. Villa’s main marksman drove the ball into the bottom corner to round off an incisive move and register his 27th goal of the season. After taking momentum into the break, the hosts required just seven second-half minutes to wipe out the Olympiacos lead. Moussa Diaby raced onto Bailey’s pass to squeeze the ball in at the near post from a narrow-angle.Despite being in the ascendancy, Villa gave the Greek side the chance to restore their advantage when Douglas Luiz was penalised for a handball in the box. Buoyed from his first-half efforts, a confident El Kaabi stepped up to dispatch the subsequent spot-kick to wrap up his hat-trick. Sensationally, Santiago Hezze restored Olympiacos’s two-goal lead in the 67th minute, with his deflected strike wrong-footing Olsen in the Villa goal.Villa’s disappointing evening was compounded when Luiz’s penalty clipped the outside of the post to ensure the visitors returned to Greece with a useful two-goal cushion. Unai Emery’s troops will now have a mountain to climb in next week’s away leg after losing a European home game for the first time this season.UEFA CONFERENCE LEAGUESemifinals – first legThursdayFiorentina – Club Brugge 3-2 (2-1)/Sottil 5, Belotti 37, Nzola 90+1 – Vanaken 17 pen, Thiago 63/Aston Villa – Olympiakos 2-4 (1-2)/Watkins 45+1, Diaby 52 – El Kaabi 17, 29, 56 pen, Hezze 67/