Mikel Arteta press conference after Liverpool 0-1 Arsenal
Dowman was absent from the Gunners’ win over Liverpool at Anfield as he started a three-match suspension.
That ban only applies domestically and so Dowman is in contention to feature in the Czech Republic, where Arteta is expected to rotate his side.
Saliba travelled with the squad on Tuesday afternoon as he pushes to show he is ready to make his first appearance of the season.
The Frenchman is back in training and has completed his rehabilitation from the back injury that has kept him out for the entire campaign so far, and Arteta said at his pre-match press conference that Saliba is “ready to go”.
"Now he's in. He's in like anybody else. All the preparation has been done to make sure all the load and all the steps have been done to minimise the risk.
"He's in a really good place, he's built the capacity that we needed. Now it's about giving him minutes.”
Ben White is likely to start, as Arteta continues to split the right-back minutes, while Cristhian Mosquera could come in to allow Ezri Konsa a rest.
The same goes for Piero Hincapie at left-back, with Arsenal keen to manage Riccardo Calafiori's workload.
In midfield, Myles Lewis-Skelly and Mikel Merino will hope to start and there is a decision for Arteta to make over whether to rest Declan Rice.
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The Arsenal boss could start him and then bring him off if the match situation is comfortable in the second half.
Eberechi Eze has been dealing with a minor injury but that is not expected to be an issue in Prague and he is set to start on the left, with Christos Tzolis only just back from a hamstring issue and unlikely to start twice in four days.
Kai Havertz took his chance up front at Anfield by scoring the winner, but Viktor Gyokeres has started two of Arsenal's three Champions League matches and is expected to lead the line here.
Predicted Arsenal XI (4-2-3-1): Raya; White, Mosquera, Gabriel, Hincapie; Rice, Lewis-Skelly; Dowman, Merino, Eze; Gyokeres
Injured: Saka
Doubt: Saliba
Venue: Fortuna Arena
How to watch: TNT Sports