In a test for both teams and the strained French police, Paris Saint-Germain hosts Barcelona in a Champions League showcase against the backdrop of violent unrest across France.
PSG and Barcelona head the standings, though Liverpool or even surprising Stuttgart could end Tuesday on top of the table.
The game, which will need a robust security presence, takes place in a very different context to when PSG beat Manchester City 4-2 away last week.
What began in France as protests against school conditions has expanded to include a wide range of other groups and causes. There have been violent clashes, fires and looting.
An emergency meeting with top government officials on Monday confirmed PSG-Barcelona and other soccer games in European competitions can go ahead after the possibility of calling off games and other big events was discussed.
Liverpool could go top with a win over Villarreal if PSG and Barcelona draw, or on goal difference if Andoni Iraola's team can rout its Spanish opposition. Stuttgart has won both of its games but Atletico Madrid will be sterner opposition for the German team.
Man City aims to get back on track after last week's PSG loss when it faces Greece's AEK Athens, while troubled Napoli seeks a first point against Norway's Bodø/Glimt.
Also, Roma plays Slovan Bratislava, Borussia Dortmund heads to Azerbaijan to face Sabah, Porto hosts PSV Eindhoven and Fenerbahce takes on Slavia Prague.