Manchester United visit Lille in the Champions League on Wednesday with manager Alex Ferguson under extreme pressure following Saturday's 4-1 thrashing at Middlesbrough.
Only three points separate the four teams in Group D and a win for leaders United in Paris would put the 1999 winners within sight of a place in the last 16.
Anything less, though, could see them deposed at the top by either Benfica or their Spanish guests on Wednesday, Villarreal.
While United's progress is uncertain, a place in the knockout phase with two games to spare is on offer for Bayern Munich, Arsenal and Barcelona.
Bayern visit Juventus knowing a repetition of their victory two weeks ago over the Italians, who lost their first Serie A match of the season at the weekend, will give them an unassailable 12
Arsenal will also confirm their place in the last 16 should they dispatch Group B's bottom club Sparta Prague at Highbury to make it four wins out of four.
Both Bayern and Arsenal could also go through with draws if other results go their way.
In Group C Barcelona have only have seven points but another three at home to third-placed Panathinaikos will assure them of progress.