For a moment, the women's football world thought Olympique Lyonnais were finally going to be knocked off their throne when the champions looked to be without Sarah Bouhaddi, Dzsenifer Marozsan, Lucy Bronze and Alex Greenwood.
It wasn't until July 10 that UEFA allowed for teams to sign up to six new players to their roster for the upcoming eight day tournament in San Sebastian and Bilbao, Spain.
Before this decision, each squad had to play with the players that were registered prior to April when the original quarter-finals were set to be played.
As per usual in the football market, clubs lost players to summer transfers and ends of contracts and just for a moment, it seemed like an underdog club could come out on top.
Lyon looked to be without four starters, Atletico Madrid without their two starting keepers and clubs looked to rely on their academy players for depth in squad.
But squads are back to some normality and some might be stronger than they were before, but lifting the trophy seems more challenging than ever, even for Lyon.
The UWCL fixtures are as follows:
- Arsenal vs PSG
- Glasgow City FC vs VFL Wolfsburg
- Olympique Lyonnaise vs Bayern Munich
- Atletico Madrid vs Barcelona
Out: Emma Mitchell (Reading), Danielle Carter (Reading), Katrine Veje (FC Rosengård), Pauline Peyraud-Magnin (Atletico Madrid), Louise Quinn (FC Fiorentina)
In: Steph Catley (Melbourne City FC), Lydia Williams (Melbourne City FC), Noëlle Maritz (Wolfsburg), Malin Gut (Grasshopper)
Caitlin Foord will have her long awaited Champions League debut after signing in the January transfer window.
The Australian managed to play just two games with Arsenal before the season was curtailed in April, and is now making her debut alongside her Matildas teammates, Catley and Williams.
Arsenal lost three starters - Veje, PPM and Quinn - from their last UWCL match in October against Slavia Prague.
Out: Katarzyna Kiedrzynek (Wolfsburg), Hannah Glas (Bayern Munich), Lina Boussaha (Le Havre), Célina Ould Hocine (Paris FC), Ève Périsset (Bordeaux)
In: Ramona Bachmann (Chelsea), Charlotte Voll (Sand), Bénédicte Simon (Reims)
Luana was signed during the January transfer window and has not yet featured in the UWCL with the Paris side; she previously made her UWCL debut with Norwegian club, Avaldsnes Idrettslag.
Bachmann is one to watch against Arsenal, the forward has had success over the Londoners on several occasions while playing for Chelsea in the FA WSL.
PSG were close to overtaking the reigning champions of Division 1, Lyon, before the season was curtailed in April and decided on points per game, finishing just three points off the leaders.
Out: Hedvig Lindhal (Atletico Madrid), Noëlle Maritz (Arsenal), Claudia Neto (ACF Fiorentina), Sara Björk Gunnarsdóttir (Lyon), Kristine Minde (Rosenborg)
In: Pauline Bremer (Manchester City), Lena Oberdorf (Essen), Kathrine Hendrich (Bayern Munich), Katarzyna Kiedrzynek (PSG)
The reining champions of the Frauen Bundesliga are emerging as favourites to take the trophy from Lyon.
They are just one of two teams left in the UWCL who completed their season (the other being Bayern Munich) and played competitively until the end of June.
Glasgow City FC
In: Janine van Wyk (Fortuna Hjørring), Krystyna Freda (Apollon), Zaneta Wyne (Klepp IL)
The only way that the club could continue to compete in the UWCL amid the pandemic was from a donation from James Anderson.
The Scottish side are proud to be taking the pitch up against one of the best with their new singings, with particular attention to the top singing of South African international Van Wyk.
Out: Lisa Weib (Aston Villa), Eva Kouache (Metz)
In: Sara Björk Gunnarsdóttir (Wolfsburg), Assimina Maoulida (US Orléans), Lola Gallardo (Atletico Madrid), Sakina Karchaoui (Montpellier), Emelyne Laurent (Bordeaux), Ellie Carpenter (Portland Thorns), Jodie Taylor (OL Reign)
Lyon gained major reinforcements in all positions, with their most notable ones being Karchaoui and Taylor.
The young French fullback fits perfectly with the champions' way of playing with high and overlapping fullbacks.
Taylor is looking to challenge her Lionesses teammate Nikita Parris, as the team's main goal scorer during her short-term loan from OL Reign in the NWSL.
But, both Bouhaddi and Marozsan's summers transfers fell through and the duo signed new long-term contracts with Lyon.
Bronze and Greenwood signed (very) short term contracts just to the end of August, when the final of the 2019/20 UEFA Women's Champions League is set.
Out: Melanie Leupolz (Chelsea), Kristin Kögel (Bayern Leverkusen), Kathrin Hendrich (Wolfsburg), Emily Gielnik, Dominika Skorvankova (Montpellier), Barabara Brecht (Essen), Mandy Islacker (FC Cologne)
In: Viviane Asseyi (Bordeaux), Sarah Zadrazil (Turnine Postdam), Hannah Glas (PSG), Lea Schüller (Essen), Marian Hegering (Essen), Klara Bühl (SC Freiburg)
Bayern have lost four of their starters, Hendrich, Gielnik, Skorvankova, and Leupolz (captain), from their last UWCL match against BIIK-Kazygurt.
Having finished their Frauen Bundesliga season at the end of June, most of the squad have a fitness advantage over their opponents Lyon, but will look to replace a lot of their league squad with new signings for the UWCL.
Out: Carla Armengol (Sevilla), Cláudia Pina (Sevilla), Candela Andújar (Valencia), Aída Esteve (Eibar), Pamela Tajonar (EDF Logroño), Stefanie Van der Gragt (Ajax)
In: Giovana Queiroz (Madrid CFF), Cata Coll (Sevilla)
Ana Cronogorcevic was signed during the January transfer window from Portland Thorns and will make her first appearance in the UWCL with the Catalan side.
Prior, the Swedish defender appeared in two UWCL finals, 2012 and 2015, with FFC Frankfurt and won the trophy in 2015 against PSG.
Barca have the fewest new singings and retain most of their squad that has used this season to grow from the 4-1 defeat to Lyon in the 2019 UWCL final.
Out: Lola Gallardo (Lyon), Kenti Robles (Real Madrid), Pau (Sporting Huelva), Carolina Arias, Olga Garcia (EDF Logroño), Sari van Veenendaal (PSV)
In: Hedvig Lindahl (Wolfsburg), Turid Knaak (Essen), Pauline Peyraud-Magnin (Arsenal), Alia Guagni (ACF Fiorentina), Merel van Dongen (Real Betis)
Deyna Castellanos was signed in the January transfer window and will play in her first UWCL after leaving FSU to sign her first professional contract in Madrid.
Atleti have lost both of their starting keepers in this transfer window, but have replaced the spots with world class keepers coming from UWCL rivals, Wolfsburg and Arsenal.