The game will take place in Athens due to current coronavirus travel restrictions and Partey has been building up his recovery from a hamstring injury in recent days.
Rob Holding (concussion) will not be available as the Gunners look to secure safe passage to the next round having drawn the first leg 1-1.
The former Atletico Madrid man has played a key role for Mikel Arteta when fit, but Thomas has been consistently hampered by injury lay-offs since arriving at the start of the season.
He has played a total of 16 games this season, just over 1,000 minutes in all competitions - but just one of those appearances have come in the Europa League from Arsenal’s seven fixtures due to injury and rotation.
Dani Ceballos and Granit Xhaka have paired up in midfield in the 27-year-old’s absence and they are the likely starters against Benfica once more.
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