Arsene Wenger is reportedly keen to strengthen at the back, after another defensive calamity cost the Gunners precious points against Liverpool last night.
The Arsenal boss is planning a late swoop for a centre-back - Marseille defender Nicolas N'Koulou is thought to be the main target - while Santos could be shown the door at the Emirates Stadium.
The Brazilian endured another rough night after replacing the injured Kieran Gibbs in the first-half of Arsenal's match against Liverpool, and Wenger is believed the be ready to cut the former-Fenerbahce left-back loose.
The Turkish club could take Santos back, according to the report, if they can match his Arsenal wages.
First-choice left-back Gibbs picked up a thigh injury against Brendan Rodgers's side, leaving Arsenal short of defensive options - but Wenger is thought to be prepared to use Thomas Vermaelen as cover at left-back.
As for potential incoming transfers, the report claims the Gunners are looking to Ligue 1 for reinforcements, with Marseille's N'Koulou top of the wishlist.
The 22-year-old defender is highly rated in France, and has been scouted by the Gunners on several occasions.
After coming through the academy at Monaco, the young defender joined Marseille in 2011, and he's since established himself at the heart of the French side's defence.