The centre-back has been a mainstay in the Gunners' defence and missed just one of their Premier League matches all season.
However, Saliba was not named in the starting XI or on the bench for the 2-2 draw against Aston Villa, prompting Arsenal to explain the absence on social media.
Writing on X, formerly known as Twitter, the club wrote: "William Saliba misses out with a minor issue."
Arteta elaborated post-match, saying: "Tomorrow we will have more information.
"Another test on him. For sure [we are worried]. Very worried."
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Jurrien Timber replaced Saliba in the Arsenal defence and played alongside Gabriel.
Myles Lewis-Skelly was rewarded for his fine form with another start whilst Kai Havertz led the attack.
Saliba is one of a number of injury issues that have affected Arsenal in recent weeks.
Gabriel Jesus was revealed to have to sustained a blow to his anterior cruciate ligament during the week.
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Bukayo Saka is still out of action with a hamstring issue alongside knee injuries to Ben White and Takehiro Tomiyasu.
Another absentee is Riccardo Calafiori with a muscle problem.
Arsenal hoped to capitalise on their north London derby win over Tottenham during the week with a win this weekend.
However, they dropped more points in the Premier League title race by squandering a 2-0 lead at home.
Gabriel Martinelli opened the scoring before Havertz doubled their lead early in the second half to put them in control.
However, Youri Tielemans and Ollie Watkins ensured Villa clawed their way back into the match.
Arsenal thought they had won it through a Mikel Merino strike but it was disallowed for handball by Havertz.
The Gunners are now six points behind leaders Liverpool, who won 2-0 against Brentford earlier in the day and have a game in hand.
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