The Spaniard joined the Gunners from their inner-city rivals on an initial season-long loan with an option to buy over the summer.
Raya signed a new deal with Brentford before joining Mikel Arteta's men, where he looks to have established himself as the club's number one.
Can David Raya play against Brentford?
Unlike in the Premier League, the Carabao Cup has no specific rules against loan players facing their parent clubs.
Instead, the EFL leave it to the clubs to find an agreement.
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So some teams are fine with it, and others aren't.
This means that if Raya is to face Brentford, the west London-based team must give their permission.
And the good news for Gunners fans is that the Bees have granted the 28-year-old permission to play against them this week.
This is because both sides consider this 'loan' to be a permanent transfer, and it has only been structured this way to help Arsenal with Financial Fair Play regulations.
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The Bees and Gunners agreed before the cup draw that Raya would be allowed to face his parent club should they face each other in the FA or Carabao Cup.
However, after being dropped for the last three games, Aaron Ramsdale will hope that he gets the nod for this one.
Arteta now has two top goalkeepers in Raya and Ramsdale and has indicated that he will be rotating them throughout the season, so if the former Sheffield United shot-stopper doesn't start here, he might start to wonder what's going on.