The 25-year-old clutched his left thigh after falling while attempting a pass and was replaced by Eberechi Eze.
"When a player has to come off with sharp pain it is never good news. We have to wait and see," Arteta told TNT Sports.
"He doesn't look good at all, but we'll have to wait and see."
Saka missed seven games last season with an Achilles problem and had hamstring surgery in December 2024, which sidelined him for more than three months.
Arsenal can ill afford to lose another winger after Christos Tzolis picked up a hamstring injury on international duty.