Will Zenit make the impossible possible?
Germany's Werder Bremen and Marseille of France are the first through to the UEFA Cup last eight, after surpassing St.Etienne and Ajax respectively. The remaining six quarter-finalists will be decided on Thursday night.
UEFA Cup holders Zenit face an uphill task if they're to stay in this year's competition, as they head into Thursday's return leg with Italy's Udinese trailing by two goals to nil.
The St. Petersburg side were undone by two late goals in the opening leg in Italy, which left Dick Advocaat's side needing at least a 2-0 win just to level things. While an Udinese goal would leave the Russians needing a massive four goals to reach the quarter-finals.
Zenit can take heart from having overturned a similar deficit when beating Marseille in last year's competition.
They will, though, have to do without defenders Aleksandr Anyukov and Roman Shirokov.
Udinese are missing a defender of their own – Maurizzio Domizzi – who is suspended.
Also looking to make it through to the quarter-finals are CSKA Moscow.
They will be in for a difficult evening as well. They're looking to defend a 1-0 advantage in Ukraine when they take on Shakhtar Donetsk.