Spain's Champions League reign under threat
Neymar and Kylian Mbappe headline free-spending Paris Saint-Germain's quest to knock Real Madrid off their perch as the Champions League group stages begin on Tuesday under the shadow of infighting at the top of the European game.
La Liga president Javier Tebas has lambasted PSG's 222 million euro ($267 million) capture of Neymar from Barcelona as "financial doping" with the French giants also set to splash another 180 million on 18-year-old Mbappe next summer to make his loan move from Monaco permanent.
Spanish clubs have dominated the competition in recent seasons. Madrid has lifted the trophy in three of the last four years with that run only interrupted by Barcelona's success in 2015.
However, that dominance has been put under threat by the riches of not only PSG but a Premier League resurgence with England boasting five teams in the group stage for the first time.
PSG will be assured a red hot atmosphere to begin their European campaign at Celtic with the Scottish champions looking to spring an almighty upset.
However, it is German champions Bayern Munich, who start at home to Anderlecht, who will provide an early test of PSG's title credentials in the battle to top Group B.
Neymar's departure provoked a summer of institutional chaos at Barcelona with a public split between the club's beleaguered board and leading figures in the dressing room.
Barca president Josep Maria Bartomeu has claimed the Catalans will have a "more competitive" side this season than last despite losing Neymar after splashing out a fee that could rise to 145 million euros on 20-year-old French winger Ousmane Dembele to replace the Brazilian.
Dembele impressed in a cameo appearance as a substitute on his debut with an assist for Luis Suarez as Barca thrashed Espanyol 5-0 on Saturday.
However, Bartomeu's theory will be put under the spotlight straight away with the visit of Juventus, who dumped Barca out at the quarter-final stage 3-0 on aggregate last season.
Real shouldn't be troubled as they begin their defence of the competition at home to Cypriots APOEL Nicosia on Wednesday.
- English Renaissance -
Tottenham Hotspur and Liverpool have the toughest tasks of England's five-strong contingent looking to reassert the cash-rich Premier League on the European stage after several years of disappointing results in the Champions League.
Spurs are looking to end their Wembley hoodoo against Borussia Dortmund in a clash that will go a long way to deciding who will be Real's closest challengers in Group H.
Mauricio Pochettino's men have won just one of their last 11 outings at their temporary home before moving into a new stadium next season.
Dortmund, though, has bitter memories of Wembley themselves having lost the Champions League final in 2013 there to rivals Bayern.
Fresh from a 5-0 hammering at the hands of Manchester City, Liverpool is seeking revenge for their defeat to Sevilla in the 2016 Europa League final when Champions League football returns to Anfield for the first time in three years.
Jose Mourinho also leads Manchester United back into European football's premier club competition at home to Basel.
City travel to Feyenoord for the Dutch champions' return to the Champions League for the first time since 2001, whilst Chelsea host Azerbaijani newcomers Qarabag.
Chelsea face stiff competition to make the knockout stages with Atletico Madrid and Roma making up Group C.
Atletico travels to the Italian capital on Tuesday to begin their latest attempt at finally landing the Champions League having fallen to cross city rivals Real in the final stages of each of the past four seasons.
Two of the revelations of European football last season go head-to-head in Group G as Leipzig welcome Monaco on their Champions League debut.
Backed by energy drinks giant Red Bull, Leipzig emerged as Bayern's closest challengers in Germany.
Unlike Monaco, who have raked in over 300 million euros in transfer fees for Mbappe, Tiemoue Bakayoko, Benjamin Mendy and Bernardo Silva, Leipzig has maintained their young core in Liverpool-bound Naby Keita, Emil Forsberg and Timo Werner.