Zenit St Petersburg's grip on the UEFA Cup has already been loosened by Udinese as this year's competition finally starts to hot up, with the betting wide open.
Two goals in the last five minutes by Fabio Quagliarella and Antonio Di Natale in the first leg have given the Serie A side the edge and it will require a Herculean effort by Dick Advocaat's team if they are to progress to the quarter-finals.
However, all is not lost as last term the Russian side came back from two goals behind after the first leg to beat Marseille on away goals.
After Italy's Champions League capitulation last week, Udinese are carrying the flag for the country in Europe and could be dark horses to go all the way.
They are safely in mid-table in Serie A and have in Di Natale and Quagliarella two potential match-winners.
Manchester City showed why they are the new favourites to win the competition by strolling to a straightforward 2-0 win against Aalborg at Eastlands last week.
However, Mark Hughes' side, for all their flair and invention, continue to be flaky in defence and that could prove crucial further down the line.
Aalborg showed little of the quality that accounted for Spain's Deportivo La Coruna in the last round and look a shadow of the side that finished above Celtic in the Champions League group stages before Christmas.
The all-Ukrainian tie is nicely poised after Dynamo Kyiv secured a 1-0 first leg victory against Metalist.
Dynamo will be confident of reaching the last eight after accounting for Valencia in the last round. They won 2-0 in a league game at Metalist earlier this month and have built up a commanding lead in the table.
The third Ukrainian team left in the competition, Shakhtar Donetsk, have a good chance of moving into the quarter-finals after only losing 1-0 at highly fancied CSKA Moscow in the first leg.
Shakhtar have drawn too many games to challenge for the Ukrainian league title this term and have saved most of their best performances for Europe, beating Tottenham in the last 32 round.
The two German sides still left in the competition, Hamburg and Werder Bremen, face difficult second leg trips after tight games at home.
Hamburg may be challenging for the Bundesliga title but could only draw 1-1 with Galatasaray, who are struggling in the Turkish League, while Werder edged a 1-0 win against a St Etienne team that is struggling to avoid relegation from the French League.
Marseille are seeking glory on two fronts and are pushing Lyon hard at the top of Ligue One, but they conceded what could prove to be a crucial away goal in the 2-1 victory against Ajax last week.
Finally Braga are one of the surprise packages in the last 16 and continued their fine run with a goalless draw at Paris St Germain in the first leg.
After Sporting Lisbon's embarrassing Champions League exit against Bayern Munich, they are doing their best to restore faith in Portuguese football.