The tournament is now in a straight knockout format which takes place all the way until the final in Leipzig in May.
Ahead of Thursday's crucial second leg, here's a reminder of the crucial rules and what comes next after the play-off round.
- Tickets available for Thursday night's second leg.
- How to watch & follow the second leg at Selhurst Park.
How many substitutes can be used?
As with the Premier League, five substitutes are permitted per team, across the 90 minutes. However – as asked by Oliver Glasner in his pre-match press conference on Thursday – both sides can use a sixth substitute if the tie goes to extra-time.
Is VAR in operation?
Yes. VAR will be in full operation as it will be for the rest of the competition. It was used last week in the first leg for a potential penalty review for the hosts in the second-half.
Who is the referee?
Luis Godinho from Portugal will be the man in the middle on Thursday evening.
Fellow countrymen Pedro Almeida and Rui Teixeira will be assisting him, with Fabio Verissimo the fourth official, and André Narciso and Bruno Esteves running the VAR.
