Nenad Bjelica's men must triumph at the Dragao to keep their hopes of making the last 16 alive, while the hosts are hoping to overtake second-placed Zenit.
The Austrian champions are yet to make an impact in the competition proper, failing to find the net in four Group G matches and claiming a solitary point on the back of a goalless draw at Zenit on matchday two.
It leaves Nenad Bjelica's team bottom of the pile and facing the ignominy of becoming only the third outfit to exit Europe's premier club competition without registering a goal, after Deportivo La Coruna and Maccabi Haifa in 2004 and 2009, respectively.
Even three points in Portugal will not be enough for Vienna if Zenit triumph at home to already qualified group leaders Atletico Madrid.
But if Diego Simeone's men do not take their foot off the gas and Vienna overturn the odds at the Estadio do Dragao, a winner-takes-all showdown with the Russian side will close the group in the Austrian capital.
Bjelica returns to the dugout following a touchline ban last time out, but two of his players, Philipp Hosiner and Christian Ramsebner, are walking a disciplinary tightrope having already collected two bookings in the group stages, with three cautions triggering a suspension.
Owing to its previous European pedigree, Porto's campaign has been perhaps more disappointing.
Paulo Fonseca's side has not been able to recreate its formidable domestic home form, with Zenit and and Atletico both leaving the Dragao three points better off – a feat not achieved by a Portuguese side in league action for an astonishing 77 matches.
The run equals Porto's worst home start to a Champions League group phase. Porto lost back-to-back matches on its own patch to Sparta Prague and Real Madrid in 2001 before overcoming Panathinaikos at the third time of asking.
Anything other than repeating that sequence against shot-shy Vienna is likely to end its participation this time around and any victory for Zenit must be matched, with Porto currently on four points to its rivals' five.
Much will rest on in-form frontman Jackson Martinez, who has 11 goals in all competitions this season.
Attacking midfielder Juan Quintero is back in training after a fortnight on the sidelines with a thigh injury and Hector Herrera returns from suspension, although left back Alex Sandro will suffer a similar fate if he collects a third yellow card of the competition.