Arsenal defender Andre Santos has been ruled out for around three months with an injury to his right ankle.
The left-back sustained the problem in last week's 3-1 Champions League defeat against Olympiacos in Greece.
A statement on the club's official website, www.arsenal.com, read: "We 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 Olympiacos last week."
The statement continued: "Andre will have surgery in Brazil this week and is expected to be out for around three months. Everyone at the club wishes him well."
The 28-year-old Brazilian joined the club in August and has made 14 appearances, scoring in the 5-3 Barclays Premier League win at Chelsea and the 2-1 home defeat of Olympiacos in north London.