The 27-year-old has been a cornerstone of Arsenal's defence this season, forming a formidable partnership with Frenchman William Saliba.
Their pairing has seen the Gunners concede just five goals in 11 Premier League matches, a record that has propelled them to the top of the table, four points clear of second-placed Manchester City.
Gabriel's absence is a setback, particularly given his aerial threat from set-pieces, but Arsenal have several options to cover, including close-season signings Cristhian Mosquera and Piero Hincapie.
"Gabi unfortunately picked up an injury with the national team. He will be out for weeks," Arteta told reporters on Friday. "We need to have another scan next Wednesday. We will have the timeline much more clearly than we have at the moment.
"It's clearly a blow. It's our leader in our backline. To miss him is never a positive thing. The good thing is we have some very good options. They need to stand up now."
Defender Riccardo Calafiori has yet to train, having withdrawn from the Italy squad with a hip problem. Arteta remained tight-lipped about the 23-year-old's availability for the clash at the Emirates.
"He missed the (Italy) games. He wasn't available. He's been carrying a few things. We had to bring him back. He hasn't trained yet. We have another session tomorrow. Let's see," the Spaniard said.