Liverpool and Barcelona are leaving it late to secure automatic qualification to the Champions League round of 16.
With just two rounds remaining, the defending champions of England and Spain currently sit outside of the top eight spots that will advance automatically.
Teams placed from nine to 24 enter a two-legged playoff to go through to the round of 16.
Liverpool topped the league phase last year, but then faced the daunting task of playing eventual winner Paris Saint-Germain in the last 16. Arne Slot's team is going a different way about it this time around and may have to navigate a playoff to advance.
Liverpool is away to Marseille on Wednesday and could be boosted by the return of Mohamed Salah from the Africa Cup of Nations. He headed off to represent his country last month after a public row with Slot raised doubts about his future.
Salah was unhappy with his lack of game time and aired his views in an explosive interview. He returns to Liverpool at a time when the Merseyside club needs more firepower following injury to record signing Alexander Isak and Hugo Ekitike, who has only recently returned to action.
Barcelona was runner-up to Liverpool during the league phase last year and progressed to the semifinals before losing to Inter Milan.
Now it is playing catch up as it heads to Slavia Prague.
Chelsea's new coach Liam Rosenior takes charge of his first Champions League game with the club at home to Pafos.
Rosenior replaced Club World Cup-winning coach Enzo Maresca this month after leading Chelsea's sister club Strasbourg to the top of the third-tier Conference League standings.
Bayern Munich — one of this season's favorites — hosts Union Saint-Gilloise.
