Image source, Getty Images

Bayer Leverkusen are experiencing one of the all-time great seasons.

They are unbeaten in all 48 games this season in all competitions, have won their first ever German title, are in the German Cup final and are 90 minutes away from the Europa League final.

Xabi Alonso's side are five games away from the first ever unbeaten season by a team in European competition.

They could break Benfica's record today of longest unbeaten run - 48 games between 1963 and 1965 - by a European top-flight side since World War II.

But after the first leg Leverkusen midfielder Amine Adli said: "If we have to lose some games, such as the second leg 1-0, we will not say no if it takes us to the final."

Image source, Rex Features

Aston Villa beat Brighton 2-1 on the final day of last season to hold off Tottenham, finish seventh in the Premier League and qualify for a European campaign for the first time after a 13-year absence.

And what a journey it has been. John McGinn scored deep into injury time to see off Bosnia-Herzegovina side Zrinjski Mostar, Villa then topped the group and thrashed Ajax in the last 16 before a nerve-shredding penalty shootout success against Lille in the quarter-finals.

These are Villa's results in Europe this season.

Group stage

• Legia Warsaw 3-2 Aston Villa
• Aston Villa 1-0 Zrinjski Mostar
• AZ Alkmaar 1-4 Aston Villa
• Aston Villa 2-1 AZ Alkmaar
• Aston Villa 2-1 Legia Warsaw
• Zrinjski Mostar 1-1 Aston Villa

Last 16

• Ajax 0-0 Aston Villa
• Aston Villa 4-0 Ajax (Villa won 4-0 on aggregate)

Quarter-final

• Aston Villa 2-1 Lille
• Lille 2-1 Aston Villa (2-2 on aggregate, Villa won 4-3 on penalties)

Semi-final

• Aston Villa 2-4 Olympiakos

Mike: I'm staggered that this is being described by some as Villa's biggest game of the season. The biggest game will be the one where they qualify for the Champions League, not getting to the final of a very mediocre competition.

Ask West Ham fans what winning this tournament meant to them.

Neil Lennon
Former Celtic manager on BBC Radio 5 Live

We are all set for a great European night. We arrived around two and a half hours before kick off and the fans were already here making a lot of noise, so the atmosphere is bubbling under already. The pitch is immaculate and there is a real sense of anticipation growing around the stadium.

Get in touch throughout the course of tonight to let us know your thoughts on the Europa League and Europa Conference League action.

Will Aston Villa overturn the two-goal deficit in Greece? Will Bayer Leverkusen make it 49 games unbeaten? Can Marseille take a step closer to regaining the trophy they won in 2018?

Get in touch via the means above.

BBC Radio 5 Live

We are up and running with the build-up to our live commentary on BBC Radio 5 Live so press the play button at the top of this page to listen along.

Bayer Leverkusen manager Xabi Alonso has made six changes to the side which beat Eintracht Frankfurt 5-1 in the Bundesliga at the weekend.

Matej Kovar starts in goal ahead of regular number one Lukas Hradecky, while Jonathan Tah returns to captain the side in central defence.

Wing-backs Jeremie Frimpong and Alex Grimaldo are also back in the team with Arthur and Nathan Tella benched. Florian Wirtz is also a sub, despite being rested on Sunday.

Bayer Leverkusen XI: Kovar; Hincapie, Tah, Tapsoba; Frimpong, Xhaka, Palacios, Grimaldo; Hofmann, Adli, Hlozek

Subs: Hradecky, Lomb, Stanisic, Kossounou, Andrich, Borja Iglesias, Wirtz, Arthur, Schick, Tella, Boniface, Puerta

Image source, Opta

There are four changes to the Roma side which started their 1-1 Serie A draw with Juventus.

Gianluca Mancini comes in at centre-back in place of the benched Diego Llorente, while Sardar Azmoun and Stephan El Shaarawy flank Romelu Lukaku up top.

Pablo Dybala drops to the subs, alongside English duo Chris Smalling and Tammy Abraham.

Roma XI: Svilar; Spinazzola, Ndicka, Mancini, Angelino; Cristante, Pellegrini, Paredes; Azmoun, Lukaku, El Shaarawy

Subs: Rui Patricio, Karsdorp, Smalling, Abraham, Diego Llorente, Celik, Renato Sanches, Dybala, Aouar, Baldanzi, Bove, Zalewski

Image source, Opta

Atalanta make five changes to the side who beat Salernitana 2-1 in Serie A on Saturday.

Juan Musso starts in goal with Berat Gjimshiti, Teun Koopmeiners, Matteo Ruggeri and Charles De Ketelaere coming back into the team.

Atalanta XI: Musso, De Roon, Hien, Gjimshiti, Zappacosta, Koopmeiners, Ederson, Ruggeri, De Ketelaere, Scamacca, Lookman.

Subs: Carnesecchi, Rossi, Pasalic, Toure, Bakker, Adopo, Hateboer, Scalvini, Bonfanti, Palestra, Comi, Miranchuk.

Marseille have three changes to the side who drew 1-1 with Atalanta in the Europa League semi-final first leg tie.

Quentin Merlin, Samuel Gigot and Iliman Ndiaye have been selected to come into the starting line-up.

Marseille XI: Lopez, Mbemba, Gigot, Balerdi, Merlin, Clauss, Veretout, Kondogbia, Ndiaye, Aubameyang, Harit.

Subs: Ngapandouetnbu, Blanco, Ounahi, Moumbagna, Meite, Correa, Sarr, Soglo, Henrique, Lafont, Daou, Murillo.

Image source, PA Media

Aston Villa must handle a "difficult" atmosphere in their "biggest game of the season" as they look to come from behind against Olympiakos, says manager Unai Emery.

The Premier League side headed to Piraeus trailing 4-2 following the first leg of their Europa Conference League semi-final at Villa Park.

Emery admitted his side would have to be much improved to reach the final.

The former Sevilla and Arsenal boss said: "We must do better. It will be difficult with the atmosphere. We need to build a new experience here with our players and our idea. This is the biggest game of the season."

Three matches, three venues, three places in European competition finals up for grabs.

Image source, Getty Images

Image source, Getty Images

Image source, Getty Images

Image source, PA Media

All matches start at 20:00 BST.

Europa League semi-finals

• Atalanta v Marseille (1-1 after first leg)
• Bayer Leverkusen v Roma (2-0 after first leg)

Europa Conference League semi-final

• Olympiakos v Aston Villa (4-2 after first leg) - winner plays Fiorentina in the final.

Olympiakos haven't played since the first leg and make just one change with full-back Quini replacing the injured Francisco Ortega.

Ayoub El Kaabi, who scored a hat-trick last week, starts up top.

Olympiakos XI: Tzolakis: Quini, David Carmo, Retsos, Rodinei: Chiquinho, Iborra, Hezze; Fortounis, El Kaabi, Podence.

Subs: Paschalakis, Papadoudis, André Horta, El-Arabi, Alexandropoulos, Masouras, João Carvalho, Jovetić, Apostolopoulos, Prekates, Ntoi.

Aston Villa make two changes from the side that lost 1-0 to Brighton at the weekend.

World Cup winner Emiliano Martinez returns in goal, with back-up keeper Robin Olsen dropping to the bench.

Martinez was suspended for the first leg and was not in the squad for Villa's Premier League loss on Sunday.

Matty Cash is also in the starting XI, with Morgan Rogers unavailable through injury.

Aston Villa XI: Martinez; Cash, Diego Carlos, Konsa, Torres, Digne; Diaby, McGinn, Douglas Luiz, Bailey; Watkins.

Subs: Gauci, Olsen, Lenglet, Duran, Hayden, Iroegbunam. Patterson, Munroe, Kellyman, Young.

Olympiakos took control of their Europa Conference League semi-final, winning 4-2 at Villa Park in the first leg against Aston Villa.

Ayoub El Kaabi scored a hat-trick for the visitors, netting twice early on.

Ollie Watkins reduced the deficit for Unai Emery's side and Moussa Diaby equalised moments after the interval.

Olympiakos roared back in front with an El Kaabi penalty and a deflected strike from Santiago Hezze.

Douglas Luiz missed a late penalty, meaning Villa must overturn a two-goal deficit in the second leg in Piraeus on 9 May to reach their first European final since 1982.

Image source, Getty Images

We'll have Aston Villa's full team with you shortly, but we can tell you already that goalkeeper Emiliano Martinez is starting for the visitors.

Hello and welcome along to BBC Sport's coverage of tonight's European football as Aston Villa look to overturn a two-goal deficit and advance into the Europa Conference League final.

We have live commentary on BBC Radio 5 Live, which you can listen to in this very page with kick-off at 20:00 BST.

It has been a brilliant season for Aston Villa, with them currently on course to qualify for next season's Champions League.

But a bad night at the office last week left them facing an uphill task if they are to reach their first European final since 1982.

Unai Emery's side need to score at least twice away at Olympiakos if they are to have any hope of reaching the Europa Conference League final.

Image source, Rex Features