Who will Liverpool, Arsenal and Villa play?
Those finishing in the top eight automatically progress to the last 16, where they will be seeded.
They will await the winners of eight two-legged knockout play-off ties featuring the clubs ranked from ninth to 24th.
Liverpool could possibly face the following four teams - PSG, Benfica, Monaco or Brest.
Arsenal could possibly face the following four teams - AC Milan, PSV, Feyenoord or Juventus.
Aston Villa could possibly face the following four teams - Atalanta, Borussia Dortmund, Sporting Lisbon or Club Brugge.