Arsenal pair Mikel Arteta and Mathieu Debuchy have been ruled out for three months each after having surgery.
Midfielder Arteta, 32, had a bony spur removed from his left ankle, which the club said has been causing him "significant discomfort" for months.
Defender Debuchy, who just returned from three months out with an ankle injury, had an operation on a shoulder he dislocated in the win over Stoke.
Boss Arsene Wenger described Debuchy's injury on Sunday as "unbelievable".
"It's very unfortunate," said the Frenchman.
"It's unbelievable because he's had two surgeries in the same season. He just came back, he played seven games and he's out again."
Debuchy has played just 14 times since signing from Newcastle in July in a deal worth a reported £12m.
With Kieran Gibbs recovering from an inflamed heel, 19-year-old Hector Bellerin or Calum Chambers may deputise against Manchester City on Sunday.
Arsenal took the decision to send Arteta for surgery to preserve his long-term fitness.
The Spaniard last played on 26 November in a 2-0 win over Borussia Dortmund.
"He had limited mobility in his ankle and some persistent inflammation that had an impact on his calf," explained Wenger.
"That meant we had to make the decision to have surgery and it's a proper solution which gives him the best chance to recover."
Arteta has scored 16 goals in 136 appearances for Arsenal since joining the club from Everton for £10m in August 2011.
Meanwhile, Legia Warsaw said their 17-year-old midfielder Krystian Bielik will have a medical with the Gunners on Friday.
"I'm going to London to fulfil my dreams," Bielik told Legia's official club website. "I hope I will become an Arsenal player soon."
|Arsenal's injury list|
|Player||Injury||Most recent appearance|
|Mikel Arteta||ankle||26th Nov v Borussia Dortmund|
|Mathieu Debuchy||shoulder||11th Jan v Stoke|
|Danny Welbeck||thigh||28th Dec v West Ham|
|Kieran Gibbs||heel||1st Jan v Southampton|
|Jack Wilshere||ankle||22nd Nov v Manchester United|
|Abou Diaby||calf||23rd Sept v Southampton|
|Serge Gnabry||knee||11 March v Bayern Munich|