The duo went off with injuries in the recent win over Hull City.
They are set to definitely lose the Welshman for this weekend’s game and a period beyond that with them waiting to discover the extent of his thigh injury.
It is better news in regards to the two defenders though, with both of them passed fit for this weekend’s clash with Watford.
“Mertesacker and Gabriel are very positive, there is nothing wrong there, they are both good,” Arsene Wenger told the club’s official website.
The news will come as a big positive for Wenger given he is currently missing first choice centre back Laurent Koscielny also.
The Frenchman has been missing since picking up a thigh injury in the loss to Manchester United, and is not expected to return in time for this game.
If he had been missing Gabriel and Mertesacker it would have left him in dire straits for this weekend in particular, with just Calum Chambers available to him in the position.