There were famous wins for Arsenal FC and Tottenham Hotspur FC in the first legs of their UEFA Champions League round of 16 ties, but the question now is whether the north London pair can finish the job against FC Barcelona and AC Milan respectively.

Arsenal face undoubtedly the tougher challenge as they travel to Catalonia to defend their 2-1 lead against a Barcelona side who have won 18 of 21 home matches this season. Josep Guardiola's men crushed the Premier League team 4-1 at Camp Nou in last year's quarter-finals – Lionel Messi scoring all four – and the Argentinian international is unlikely to be as profligate as he was in the first leg, prior to Arsenal's late revival. Arsène Wenger's hopes of hurting Barça at the back on Tuesday are not helped by the absence of the injured Robin van Persie and Theo Walcott.

Tottenham wrote the most captivating page yet of the fairy tale that has been their debut campaign in the UEFA Champions League when Peter Crouch earned them a 1-0 first-leg success at a rain-soaked San Siro. The omens are positive that they can complete their assignment on Wednesday against opponents missing the suspended Gennaro Gattuso for the White Hart Lane return. Spurs have won all four home games in the competition this term while Milan have recorded only one victory in 14 previous visits to England.

Like Milan, AS Roma must overturn a deficit when they go to FC Shakhtar Donetsk on Tuesday and history is not on their side – just once in the UEFA Champions League era has a team undone the damage of a first-leg home loss. Shakhtar triumphed 3-2 in Rome to take a big step towards reaching the last eight for the first time and the Ukrainians' 11-match unbeaten home run in Europe underlines further the size of the task facing Roma's rookie coach Vincenzo Montella, who has replaced Claudio Ranieri since the opener.

The only one of this week's ties currently all-square is FC Schalke 04 v Valencia CF, although the German hosts hold a slight advantage following their 1-1 draw at Mestalla last month. Raúl González got Schalke's away goal and will attempt to inflict further punishment on his compatriots. Valencia, however, have their own causes for optimism – namely, their unbeaten away record in the group stage and the uplifting precedent of a 1-0 victory in Gelsenkirchen in the 2007/08 group stage.

Can Arsenal hold out against Barcelona? Will Milan or Roma battle back? Can Raúl take Schalke past Valencia? Have your say on this week's second legs.