Both teams required penalties to advance from the quarter-finals, with Villa edging past Lille and Olympiacos beating Fenerbahce.
Match preview
Boasting an exceptional European record with three Europa League titles and two runners-up medals to his name, Unai Emery is now targeting Conference League glory in his first full season with Aston Villa following a nail-biting two-legged clash with Lille a fortnight ago.
The Lions initially let a 2-1 first-leg lead slip against French outfit Lille, but Matty Cash restored parity to send the closely-fought tie to penalties, with Emiliano Martinez starring with two spot-kick saves to help Villa prevail 4-3 in the shootout.
Villa have put together a six-game unbeaten run in all competitions that has been bookended by Premier League draws against Brentford and Chelsea in which they let two-goal leads slip, most recently drawing 2-2 at home with the latter last weekend even though they were leading at half time.
Despite that, Emery's side remain on course to secure Champions League football for next season as they sit fourth in the Premier League table and seven points clear of fifth-placed Tottenham Hotspur, who have two games in hand but lost to rivals Arsenal last time out.
Villa's ability to balance European and domestic duties will be put to the test once again over the next seven days, and although they have never faced Greek opposition before, they will fancy their chances of securing a positive first-leg result on Thursday as they boast a 100% record across six home matches in this season's competition; they have also failed to score in just one of their last 31 European home games.
Olympiacos have progressed to their first-ever UEFA club competition semi-final after beating Turkish outfit Fenerbahce 3-2 on penalties in the quarter-finals, following a 3-3 draw over two legs.
The Red-Whites suffered a slender 1-0 second-leg defeat in Istanbul, but as they did in the previous round against Maccabi Tel Aviv, they prevailed in the shootout thanks to the heroics of goalkeeper Konstantinos Tzolakis, who saved three penalties to spare the blushes of both Youssef El-Arabi and Rodinei who failed to convert from 12 yards.
Since his appointment as manager in mid-February, Jose Luis Mendilibar has won 12 of his 17 games in charge of Olympiacos across all competitions, with his side extending their seven-game winless run last weekend courtesy of a comfortable 4-1 Greek Super League victory over Lamia.
Currently trailing in a four-way title race, 47-time Super League champions Olympiacos must put their domestic duties to one side and shift their focus to the Conference League, with Mendilibar - who led Sevilla to Europa League glory last season - tasked with steering the Red-Whites to a positive result in their tricky first-leg clash at Aston Villa.
Success in Birmingham could prove challenging, though, as Olympiacos have won just three of their previous 19 European trips to England, most recently losing 1-0 at West Ham United in the Europa League group stage in November last year - all three victories during this run have come against Arsenal.
Aston Villa Europa Conference League form:
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Aston Villa form (all competitions):
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Olympiacos Europa Conference League form:
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Olympiacos form (all competitions):
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Team News
Aston Villa goalkeeper Emiliano Martinez could reportedly be facing up to two weeks on the sidelines after being forced off at half time in last weekend's draw against Chelsea with a thigh strain.
It is thought that the Argentine will target a return for the second leg in Greece, but in the meantime, Robin Olsen - formerly of Olympiacos' rivals PAOK - is set to start between the sticks.
The Lions will also be without Boubacar Kamara (knee), Emiliano Buendia (knee), Tyrone Mings (knee), Jacob Ramsey (foot), Alex Moreno (calf) and Nicolo Zaniolo (unspecified), while Youri Tielemans, who was forced off in the first half against Chelsea with a groin injury, is a major doubt.
Moussa Diaby was brought on for Tielemans and then hooked off later in the contest following a poor display, but either the Frenchman or Jhon Duran could be handed a start in attack alongside Ollie Watkins if Villa's No.8 is not deemed fit to feature.
As for Olympiacos, Ruben Vezo, Gelson Martins and Nelson Abbey, who all featured in last weekend's win over Lamia, are ineligible to play on Thursday as they were all omitted from the Conference League squad.
Andreas Ndoj and Georgios Masouras are both suspended, the former was sent off in the second leg against Fenerbahce, but Panagiotis Retsos is available to return from a one-match continental ban and is expected to start in central defence alongside David Carmo.
Nottingham Forest loanee Omar Richards will be pushing to start ahead of Francisco Ortega at left-back, while Wolverhampton Wanderers loanee Daniel Podence could be joined in attack by Kostas Fortounis and El Kaabi, the latter has scored a team-high 27 goals in all competitions this season.
Aston Villa possible starting lineup:
Martinez; Cash, Konsa, Torres, Digne; Bailey, Luiz, McGinn, Rogers; Duran, Watkins
Olympiacos possible starting lineup:
Tzolakis; Rodinei, Restos, Carmo, Ortega; Horta, Chiquinho, Hezze; Fortounis, El Kaabi, Podence
We say: Aston Villa 3-1 Olympiacos
Ten of the last 11 games to be held at Villa Park have seen at least three or more goals scored, and another entertaining match could be in store on Thursday.
Although Aston Villa could be missing a few key players, we believe Emery still has enough quality at his disposal to steer the hosts to a first-leg victory over Olympiacos.