Arsenal duo Jurrien Timber and Thomas Partey were missing from today's open training session, according to Sky Sports.
The Gunners have had been hampered by defensive injuries and they are currently without several players for the Monaco game.
Ben White and Takehiro Tomiyasu are out with long-term injuries while Gabriel, Riccardo Calafiori and Oleksandr Zinchenko are nursing niggles.
Timber and Partey have joined the duo in the treatment room and manager Mikel Arteta has a huge selection headache ahead of tomorrow's game.
The manager has already confirmed that Kieran Tierney is braced to start at left-back while he may need to pick a makeshift option on the right.
Josh Nichols is an academy graduate who can play there, but with the importance of the fixture, Arteta could go with someone experienced.
Declan Rice could be a solution for the department, having played occasionally from the role during his formative years at West Ham.
Arsenal need a victory against Monaco in the Champions League tomorrow to boost their prospects of making the round of 16 stage directly.