Gianl-Luca Waldschmidt returned from injury in Benfica's 1-1 draw away to Moreirense at the weekend. Jardel and Andre Almeida are expected to miss out here.
Former Tottenham defender Jan Vertonghen will rekindle his old North London rivalry with the Gunners here. Arsenal will also know a lot about his defensive partner, Nicolas Otamendi from his playing days with Manchester City.
Arsenal supporters will be in for a shock if former Queens Park Rangers' trickster Adel Taarabt starts in his new defensive midfield position on Thursday.
Kieran Tierney and Thomas Partey are unlikely to recover from injury in time to face Benfica, though Mikel Arteta has confirmed the former has the best chance if either do.
Pierre-Emerick Aubameyang picked up a knock to his ankle against Leeds on Sunday but is expected to be fine to feature here if required.
Rob Holding will return to the side after dropping to the bench at the weekend. David Luiz will hope to partner him at the back to face former club Benfica.
Emile Smith Rowe has played a lot of football of late and may be given the night off, with Martin Odegaard continuing in the side.
Due to local travel restrictions imposed by Portugal, this game will staged in Rome, Italy with the return leg in Athens, Greece.
It's far from ideal for both sides, as Benfica have won 12 of their 16 home matches this season, while Arsenal now have a nightmare trip ahead of them to fit in to an already hectic schedule.
Benfica, who have dropped down from the Champions League, have only won three of their last nine matches in all competitions.
Arsenal ended a three-game winless streak and two-game losing run with a 4-2 win over Leeds at the weekend. They have lost three of their last four away from home.
Arsenal will be considered favourites over the two legs but Mikel Arteta would rather do without the new travel arrangements.
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