Arsenal manager Arsene Wenger will be without Andre Santos until March after it emerged the Brazilian left-back will undergo surgery on an ankle injury.
Santos, 28, suffered ligament damage to his right ankle in last week's 3-1 Champions League defeat to Greek side Olympiakos.
The injury was initially thought to be a minor strain that would rule the Arsenal defender out until the New Year. However, a scan revealed the damage to be much greater than previously thought and the left-back has returned to Brazil for surgery.
"Arsenal Football Club can confirm that, following investigations and subsequent medical opinions by club specialists, left-back Andre Santos will have surgery to repair ligament damage in his right ankle sustained in the game against Olympiakos last week," a club statement said.
"Andre will have surgery in Brazil this week and is expected to be out for around three months. Everyone at the club [Arsenal] wishes him well."
Wenger now faces a defensive crisis ahead of a hectic festive period with Santos, Kieran Gibbs, Bacary Sagna and Carl Jenkinson all currently injured.