Arsenal put their Premier League commitments to one side on Wednesday evening when they face a tricky trip to Portugal to take on Manuel Jesualdo Ferreira's FC Porto side at the Dragao Stadium.
Arsene Wenger's side faced the Portuguese outfit during last season's group stage and both teams safely secured their passage into the last 16.
Arsenal smashed Ferreira's beleaguered men 4-0 at the Emirates Stadium thanks to braces by Robin van Persie and Emmanuel Adebayor.
However, with van Persie nursing an ankle injury and Adebayor now at Manchester City, the Gunners will have to find goals from elsewhere. In the game at the Dragao Stadium, the hosts turned the tables, beating the Londoners 2-0.
Bruno Alves headed home to open the scoring before former striker Lisandro Lopez doubled the lead.
Wenger opted to rest many of his key first-team players, offering the likes of Johann Djourou, Aaron Ramsey, Jack Wilshere and Carlos Vela some European match-night experience.
It is safe to say he will not be considering such tactics at this crucial stage of the competition.
Porto have enjoyed life on their own patch against English sides until recently.
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They remained undefeated in 11 games - winning five and drawing six - but a majestic Cristiano Ronaldo effort saw Manchester United win 1-0 in the quarter-finals last season.
Then, in this term's group stage, Chelsea's Nicolas Anelka scored in a 1-0 success to wreck their fine record.
Elsewhere, Bayern Munich entertain Fiorentina at the Allianz Arena and, after a slow start in this season's Bundesliga, the Germans are now flying under the guidance of Louis van Gaal.
Their season turned after a stunning 4-1 away victory at Juventus that secured their passage to the last-16 at the Old Lady's expense.
With Arjen Robben and Franck Ribery causing all sorts of problems for opposing defenders, Fiorentina could be in for a tough night in Bavaria.
However, they will be buoyed by their exploits in the group stage when they qualified ahead of Liverpool.
Cesare Prandelli's men defeated the European giants at their Stadio Artemio Franchi home thanks to a Stevan Jovetic double in a 2-0 success.
With qualification already guaranteed, they then grabbed a 2-1 win at Anfield in the final round of fixtures.
After falling behind to a Yossi Benayoun header, Martin Jorgensen levelled for Viola. Alberto Gilardino's dagger-blow in the final minute secured a further win and they should take confidence ahead of the Munich clash.
Van Gaal's men are the online sportsbook favourites to secure a first-leg lead to take to Florence.