Real Madrid and Atletico Madrid begin their respective Champions League campaigns with huge tests against Paris Saint-Germain and Juventus in the pick of Wednesday's action.
Atletico will be smarting from last season's 3-2 aggregate defeat to Juve in the round of 16, when Cristiano Ronaldo – a consistent nemesis of theirs during his time in LaLiga – netted a hat-trick in a 3-0 second-leg win to see the Old Lady into the quarter-finals.
Madrid get started away to PSG, who will be aiming to continue their fine run at home in the group stage despite being without Neymar, Kylian Mbappe and Edinson Cavani.
Last term's beaten finalists Tottenham, Premier League champions Manchester City and German giants Bayern Munich are also in action.
Below, we have highlighted the key data ahead of Wednesday's contests.