Gothenburg - Arsenal face an anxious wait over the fitness of Gabriel after the defender was stretchered off in Sunday's 3-2 victory over Manchester City in a pre-season friendly in Sweden.
Sergio Aguero gave City a first-half lead in Gothenburg, but Arsenal struck back with goals from Alex Iwobi, Theo Walcott and Chuba Akpom before Kelechi Iheanacho netted a late consolation.
However, an injury to Gabriel in the closing stages could see the Brazilian ruled out of the start of the new Premier League season along with long-term absentee Per Mertesacker.
Arsenal manager Arsene Wenger said it was too early to know the full extent of the problem, but the Frenchman was clearly concerned about the health of his central defender.
"He's in pain. Let's hope the pain is not a sign of bad news," Wenger told Arsenal's club website.
"We have not even made a diagnosis in the medical room with our doctors or physios yet. I can't tell you more.
"The only thing we have to know now is how big the damage is with his ligament."
France international Laurent Koscielny is also likely to miss the Gunners' opening league game at home to Liverpool next Sunday having yet to resume full training after helping his country reach the final of Euro 2016.