Arsenal have identified RB Leipzig defender Lukas Klostermann as a priority transfer target after Gabriel picked up an ankle injury in the pre-season friendly against Manchester City.
German daily Bild says the Gunners are hot on the trail of the 20-year-old centre-back, who is currently competing in the Olympics with the Germany national team.
North London rivals Tottenham, Juventus and Ajax are also interested in the player, according to the paper.
Arsenal are light on central defenders ahead of their Premier League curtain-raiser against Liverpool on 14 August, with Laurent Koscielny and Per Mertesacker out injured and Gabriel also facing a spell on the sidelines.
Rob Holding, a £2m ($2.6m) summer signing from Bolton Wanderers, is the only fit centre-back at the Emirates Stadium.
Arsenal boss Arsene Wenger has made bids for Valencia defender Shkodran Mustafi and Lyon striker Alexandre Lacazette, with midfielder Granit Xhaka his only other senior signing so far in the summer.
Speaking after the Gunners beat City 3-2 in Gothenburg, Wenger said he did not know how serious Gabriel's injury was.
"He is in the medical team with our doctor and our physios," the Frenchman told Sky Sports.
"He's in pain and let's hope the pain is not a sign of bad news but certainly it's an ankle sprain, we just need to wait to see how bad the damage is.
"Of course we are frustrated but I've never seen an intelligent accident. We have to take that. It's part of our game."
Arsenal beat City after goals from Alex Iwobi, Theo Walcott and Chuba Akpom cancelled strikes from Sergio Aguero and Kelechi Iheanacho.
The North London club have also been linked with summer moves for Wolfsburg winger Julian Draxler – after the Germany international publicly declared that he wanted to join a "top international club" – and Leicester City forward Riyah Mahrez.