Newcastle United and Chelsea have plenty of work to do to progress from the round of 16, while Zenit are facing disaster and the likes of Tottenham and Lazio are in comfortable positions.
Rubin Kazan vs. Levante, agg. 0-0, 5pm BST, 12pm ET
Rubin secured the deadly-dull away draw they required in Spain, although at the expense of a red card to Cristian Ansaldi, who will be suspended for the home leg. The Russians will be slim favourites to progress, but this tie is very much still open.
Zenit St. Petersburg vs. FC Basel, agg. 0-2, 5pm BST, 12pm ET
Zenit are staring down the barrel of elimination after falling to a 2-0 defeat in Switzerland, although they have the quality to overturn that deficit. This could be hugely entertaining, or it could be terribly dull as Basel park the bus.
Inter Milan vs. Tottenham Hotspur, agg. 0-3, 6pm BST, 12pm ET
With a three-goal deficit to overcome and no away goals, this tie is virtually over already, and Inter will face a near-impossible task in qualifying here. Nonetheless, with Spurs having lost their last post-European domestic game, André Villas-Boas may take the opportunity to rest players, so anything is possible.
Bordeaux vs. Benfica, agg. 0-1, 8:05pm BST, 3:05pm ET
Benfica got the narrow home victory they wanted and will be favourites to progress in France, although the tie is still open. If the Portuguese score, they'll almost certainly make it through to the next round.
Chelsea vs. Steaua Bucharest, agg. 0-1, 8:05pm BST, 3:05pm ET
Chelsea suffered a 1-0 defeat in Romania and will now have a job to do in front of their own fans. Given the gulf in quality between the two sides, the Blues will still be favourites to progress, although the lack of an away goal means that if Steaua score, things could get very interesting indeed.
Fenerbahce vs. Viktoria Plzen, agg. 1-0, 8:05pm BST, 3:05pm ET
Fenerbahce got the away result in the Czech Republic, and Plzen must now win in what is a difficult away trip under any circumstances. The Turks are clear favourites here.
Lazio vs. VfB Stuttgart, agg. 2-0, 8:05pm BST, 3:05pm ET
Probably the most over of all the ties, with Lazio gaining a comfortable 2-0 win in Germany and able to field enough players to ensure they get the job done in Rome. This one is over.
Newcastle United vs. Anzhi Makhachkala, agg. 0-0, 8:05pm BST, 3:05pm ET
The first leg of this tie was a godawful, unwatchable scoreless draw, so there's everything to play for on Tyneside. Newcastle will be confident of a home victory, but there is quality in Anzhi's lineup, and the threat of an away goal will be a considerable one.