Clubs are paired based on their positions at the end of the league phase to form four seeded pairs.

That means teams who finished ninth and 10th, 11th and 12th, 13th and 14th, as well as 15th and 16th are all paired together and seeded.

The clubs that finished in the bottom end of the league phase table, 17th to 24th, form the other four unseeded pairs.

The clubs in each seeded pair are drawn into the same knockout phase bracket, where they will play against the clubs in each unseeded pair.

So, ninth seeds Lausanne-Sport and 10th seeds Crystal Palace were drawn against unseeded 23rd and 24th-placed teams Zrinjski Mostar and Sigma Olomouc.

As Mainz finished seventh and AEK Larnaca finished eighth in the league phase, they have been paired together in the same bracket for the round of 16, where they will face either Crystal Palace, Zrinjski Mostar, Sigma Olomouc or Lausanne-Sport.

Sides can face another team from the same national association in the knockout phase play-offs – although there are no other English clubs in the competition.

Clubs can also face opponents they met during the league phase.

This article is the latest from BBC Sport’s Ask Me Anything team.