The Gunners were already missing five defenders for Sunday's 1-1 draw with Fulham in the Premier League, where Oleksandr Zinchenko joined Takehiro Tomiyasu, Ben White, Gabriel Magalhaes and Riccardo Calafiori in the treatment room.
Neither Arsenal nor Arteta provided any specifics on Zinchenko's injury, although the Gunners boss said that he was hopeful of having the Ukrainian, Gabriel and Calafiori back in action against Monaco.
Gabriel has been struggling with a knock ever since the 5-1 win over Sporting Lisbon, which flared up against West Ham United a couple of weekends ago and has ruled him out of matches against Manchester United and Fulham.
Calafiori is believed to have exacerbated a previous knee problem against West Ham too, and none of the Italian, Gabriel or Zinchenko were spotted in Tuesday's pre-game training session.
Thomas Partey, Jurrien Timber join Arsenal injury list?
In addition, neither Thomas Partey nor Jurrien Timber were seen during the open part of practice, potentially depriving Arteta of the only other two senior right-back options in his ranks.
Partey was chosen to start at right-back in the clash with Fulham, where Timber operated on the left-hand side due to Zinchenko's injury, and neither man appeared to sustain an injury during the game.
However, their absences from Tuesday's training session raises serious doubts about their involvement in Wednesday's game, where long-term knee victims White and Tomiyasu will definitely be sidelined.
Arteta will be quizzed on the fitness of his squad in his pre-game press conference later on Tuesday, but the Spaniard always keeps his cards close to his chest regarding injury news and is unlikely to rule any of his doubts in or out either way.
Should neither Partey nor Timber be passed fit for the visit of Monaco, Arteta will have to get creative with his right-back selection, potentially calling on a youth player or doing some more rejigging with his senior crop.
What could Arsenal's defence look like against Monaco?
In the one piece of positive defensive news for Arsenal, William Saliba and Jakub Kiwior both appear to be fully fit and on track to start in the heart of defence in midweek, but who starts out wide is anybody's guess.
Arteta does have one other bona-fide left-back option available in the shape of Kieran Tierney, who has been an unused substitute in the Gunners' last four games after recovering from the severe hamstring injury he suffered at Euro 2024.
Tierney is not in Arteta's plans moving forward, but the Spaniard may have no choice but to throw him in from the first whistle on Wednesday, where 18-year-old Myles Lewis-Skelly is another option.
While Tierney is an experienced option on the left, Arsenal will likely have to pluck an academy graduate from the Under-21s to cover at right-back, potentially one of Josh Nichols or Josh Robinson.
Nichols played the full 90 in Arsenal's 5-1 EFL Cup win over Bolton Wanderers in September, but he was not seen in training on Tuesday either.
Written by
Ben Knapton